CML1004-Microsoft MPIO Best Practices

Dell Best Practices

Dell Compellent Storage Center - Microsoft Multipath I/O Best Practices

Kris Piepho, Microsoft Product Specialist January 2015

2 Dell Compellent Storage Center - Microsoft Multipath I/O Best Practices | CML1004

Revisions

Date Description

10/11/2010 Initial release

10/21/2011 Corrected Errors

11/29/2011 Additional content on Server Core

10/15/2012 Updated to include Windows Server 2012 content

5/29/2013 Updated to include Server 2008 R2/2012 iSCSI initiator setup and appendix listing recommended hotfixes and registry values

10/18/2013 Updated to include Windows Server 2012 R2 content

1/10/2014 Updated hotfix information

1/12/2015 Updated configuration recommendations

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THE CONTENT IS PROVIDED AS IS, WITHOUT EXPRESS OR IMPLIED WARRANTIES OF ANY KIND.

© 2015 Dell Inc. All rights reserved. Reproduction of this material in any manner whatsoever without the express written permission of Dell Inc. is

strictly forbidden. For more information, contact Dell.

Dell, the DELL logo, the DELL badge, and Dell Compellent are trademarks of Dell Inc. Microsoft®, Windows®, Windows Server®, and Windows

PowerShell® are either trademarks or registered trademarks of Microsoft Corporation in the United States and/or other countries. Other trademarks

and trade names may be used in this document to refer to either the entities claiming the marks and names or their products. Dell disclaims any

proprietary interest in the marks and names of others.


Table of contents Revisions .................................................................................................................................................................................................. 2

1 Preface .............................................................................................................................................................................................. 5

1.1 Audience ................................................................................................................................................................................ 5

1.2 Purpose .................................................................................................................................................................................. 5

1.3 Disclaimer ............................................................................................................................................................................. 5

1.4 Customer support ............................................................................................................................................................... 5

2 Introduction to Microsoft Multipath I/O .................................................................................................................................. 6

2.1 Multipath I/O overview ...................................................................................................................................................... 6

2.2 Dell Compellent Storage Center connections ............................................................................................................ 6

2.2.1 Legacy ports ........................................................................................................................................................................ 6

2.2.2 Virtual ports ........................................................................................................................................................................... 7

2.2.3 Conclusion ........................................................................................................................................................................... 8

3 Configuring servers ....................................................................................................................................................................... 9

3.1.1 Fibre Channel ...................................................................................................................................................................... 9

3.1.2 iSCSI ....................................................................................................................................................................................... 9

3.2 Automatic configuration ................................................................................................................................................. 10

3.3 Manual configuration ....................................................................................................................................................... 11

3.4 Verifying connectivity ....................................................................................................................................................... 11

3.5 Choose the I/O transport ................................................................................................................................................14

4 MPIO for Windows Server 2003 ................................................................................................................................................ 15

4.1 Dell Compellent Multipath Manager ............................................................................................................................. 15

4.2 Configuration .....................................................................................................................................................................16

4.3 Choosing a failover policy ...............................................................................................................................................16

4.4 iSCSI multipath options .................................................................................................................................................... 17

4.4.1 Installing the Microsoft iSCSI DSM ................................................................................................................................ 17

4.5 Configuring the iSCSI Initiator ....................................................................................................................................... 18

4.6 Configuring Microsoft iSCSI DSM ................................................................................................................................. 20

5 Using MPIO on Windows Server 2008 and 2008 R2 .......................................................................................................... 23

5.1 Installing the Microsoft MPIO DSM .............................................................................................................................. 23

5.1.1 Server manager GUI ......................................................................................................................................................... 23

5.1.2 Server manager CLI (2008 and 2008 R2 only) .......................................................................................................... 23


5.1.3 To install MPIO on Server Core: .................................................................................................................................... 23

5.2 Associating Dell Compellent volumes with the DSM ............................................................................................... 24

5.3 Setting the default load balance policy ....................................................................................................................... 25

5.3.1 Windows Server 2008 default load balance policy .................................................................................................. 25

5.3.2 Windows Server 2008 R2 default load balance policy ............................................................................................ 25

5.4 Per-volume load balance settings ................................................................................................................................ 26

5.4.1 Using MPCLAIM in Windows Server 2008 R2, 2012 and 2012 R2 ......................................................................... 27

6 MPIO for Windows Server 2012 and 2012 R2 ....................................................................................................................... 28

6.1 Install the Microsoft MPIO feature ................................................................................................................................ 28

6.1.1 Server manager GUI ......................................................................................................................................................... 28

6.1.2 Enable MPIO with PowerShell ....................................................................................................................................... 30

6.2 Associate Dell Compellent volumes with the in-box DSM ..................................................................................... 30

6.2.1 Using the MPIO control panel ........................................................................................................................................ 31

6.2.2 Using PowerShell .............................................................................................................................................................. 33

6.3 Set the Default Load-Balancing Policy ........................................................................................................................ 34

6.4 Per-volume load balance settings ................................................................................................................................ 35

6.4.1 Using the disk management GUI: ................................................................................................................................. 35

6.4.2 Using PowerShell .............................................................................................................................................................. 36

7 Configure a Windows 2008 R2, 2012 and 2012 R2 Server for iSCSI MPIO .................................................................... 38

7.1 Configuration .................................................................................................................................................................... 39

A Windows Server MPIO configuration recommendations for Dell Compellent Storage Center ................................ 43

B Additional resources ................................................................................................................................................................... 50


1 Preface

1.1 Audience This document was written for system administrators responsible for the setup and maintenance of

Windows® servers and associated storage. Readers should have a working knowledge of Windows and the

Dell Compellent™ Storage Center.

1.2 Purpose This document provides an overview of Multipath I/O (MPIO) and introduces best practice guidelines for

configuring MPIO on Windows Server® 2003, 2008, 2008 R2, 2012 and 2012 R2 when using the Dell

Compellent Storage Center. For installation procedures, download the MPIO Users Guide from

http://knowledgecenter.compellent.com.

1.3 Disclaimer The information contained within this document provides general recommendations. Configurations will

vary in customer environments due to individual circumstances, budget constraints, service level

agreements, applicable industry-specific regulations, and other business needs.

1.4 Customer support Dell Compellent provides live support at 1-866-EZSTORE (866.397.8673), 24 hours a day, 7 days a week,

365 days a year. For additional support, email Dell Compellent at [email protected]. Dell

Compellent responds to emails during normal business hours.

http://knowledgecenter.compellent.com/

mailto:[email protected]?subject=Dell%20Compellent%20support


2 Introduction to Microsoft Multipath I/O

2.1 Multipath I/O overview Microsoft® MPIO is a framework that allows administrators to configure load balancing and failover

processes for Fibre Channel and iSCSI connected storage devices. Load balancing can be configured to

use up to 32 independent paths from the connected storage devices.

Dell Compellent Storage Centers provide redundancy and failover with multiple controllers and RAID

modes. However, servers still need a way to spread the I/O load and handle internal failover from one path

to the next. This is where MPIO plays an important role. Without MPIO, servers see multiple instances of

the same disk device in Disk Management.

The MPIO framework uses Device Specific Modules (DSM) to allow path configuration. Currently there are

two options available:

Microsoft provides a built-in generic Microsoft DSM (MSDSM) for Windows Server 2008 and above.

This MSDSM provides adequate functionality for Dell Compellent customers.

Dell Compellent provides a DSM for Windows Server 2003.

2.2 Dell Compellent Storage Center connections Before reviewing server-specific MPIO functions, it is important to understand that various connection

options are available with the Dell Compellent Storage Center which allows multiple paths to be presented

to the servers. The following section provides a quick overview and explains the differences between

legacy port mode and virtual port mode. This overview does not take the place of the Storage Center

Connectivity Guide available on http://kc.compellent.com

2.2.1 Legacy ports In legacy mode, the front-end I/O ports are designated as either primary or reserve ports based on a fault

domain. Primary/reserved ports allow I/O to use the primary path; the reserve port is in a standby mode

until a primary port fails over to the reserve port. In terms of MPIO, this requires twice as many I/O ports to

enable multiple paths. Even more ports are required for a dual fabric. Figure 1 illustrates dual-fabric failover

ports in legacy mode.

http://kc.compellent.com/


Figure 1 Legacy primary/reserve configuration

Figure 1 shows four fault domains connected to a Series 40 Dell Compellent Storage Center with two

controller heads. Each fault domain has a primary and reserved port. For redundancy, a primary port

connects to one controller, and the reserved port in that fault domain connects to the other controller.

While this is a highly robust failover solution, it requires a large number of ports. For this reason, Dell

Compellent implemented virtual ports.

2.2.2 Virtual ports Dell Compellent introduced virtual port mode with Storage Center 5.0. Virtual ports allow all front-end I/O

ports to be virtualized. All front-end I/O ports can be used at the same time for load balancing as well as

failover to another port. Virtual ports are available for Fibre Channel connections only, iSCSI connections

only, or both Fibre Channel and iSCSI.

Fibre Channel

To use virtual ports for Fibre Channel, all Fibre Channel switches and HBAs must support N_Port ID

Virtualization (NPIV).

Figure 2 Virtual Port Configuration


Figure 2 shows a virtual port configuration. All ports of one transport type (Fibre Channel or iSCSI) are in

the same fault domain. All ports are active. If one port fails, the load is distributed between remaining

ports. Failover with this configuration uses half the ports and is just as robust as the one shown in Figure 1.

iSCSI

iSCSI follows the same wiring and port setup as Fibre Channel with the exception of the control port. iSCSI

uses a control port configured for each of the fault domains. Servers connect to the control port, which

then redirects traffic to the appropriate virtual port. When configuring MPIO, this looks slightly different

than with the legacy mode configuration because only the control port in the iSCSI Initiator software

needs to be assigned. These differences are covered below in the OS-specific sections of this document.

2.2.3 Conclusion There are two methods to enable multiple paths from the Dell Compellent Storage Center: legacy port

mode and virtual port mode. Virtual ports are preferred because they reduce the number of HBAs required

and thus reduce cost and overhead. Note that virtual ports are enabled based on protocol: virtual ports

can be enabled on Fibre Channel only, iSCSI only, or both.


3 Configuring servers Before configuring MPIO at the operating system level, first configure servers using the Dell Compellent

System Manager. The following example assumes a server has two or more Fibre Channel or iSCSI I/O

ports that are zoned or VLAN’d to see the Storage Center host bus adapters (HBAs). With Fibre Channel,

the process is the same for virtual ports as it is for legacy ports. However, with legacy ports, the server

cannot see reserve ports. iSCSI virtual ports connect only to a control port on the Storage Center.

3.1.1 Fibre Channel To create the server, properly zone the switches so that the server and controller ports are in the same

zone. The easiest way to do this is to boot the server into the card's BIOS and scan the SCSI devices on

each port. An alternate method is to preconfigure the WWNs of the HBAs in the Storage Center System

Manager.

3.1.2 iSCSI As with Fibre Channel, an iSCSI server can be created automatically or manually. For automatic

configuration, enter the IP address of the Storage Center controller HBA ports in the server iSCSI HBA or

Initiator Software. Use either the HBA BIOS or the Software Initiator configuration wizard. In virtual port

mode, enter the IP address of the control port. In legacy port mode, enter the IP address of the primary

port. This is covered in more detail in the OS specific sections. However, creating a server in the Storage

Center is the same on all operating systems.


3.2 Automatic configuration Once a server has scanned for devices or logged into the target, Storage Center automatically recognizes

the WWN/IQN. To configure a server:

1. Log in to the Dell Compellent System Manager.

2. In the tree view, right-click on Servers.

3. From the shortcut menu, select Create Server.

4. Select the appropriate HBAs and continue the wizard. If the HBA does not appear, refer to

Section 3.3, Manual configuration.

Note: If the WWN or IQN is not listed, make sure that the Only Show Up Connections box is not

checked.

Figure 3 Create Server window


3.3 Manual configuration To manually configure an HBA:

1. In the Create Server wizard shown in Figure 3, click Manually Define HBA.

2. In the Select Transport Type window, choose Fibre Channel or iSCSI.

3. Enter the WWN or iSCSI name, and click Continue. Repeat steps 1-3 for every WWN or iSCSI HBA

to be associated with the server.

4. Once all HBAs are added, check the appropriate HBA and continue the wizard.

Note: The new HBA appears with a white X in a red circle. Once the server is connected the warning

state is removed.

Figure 4 Manually defined HBA

3.4 Verifying connectivity To verify that the connectivity is correct:

1. In the tree view, select a server.

2. Click Connectivity. This window shows all paths available to the server based on the HBA and

controller ports.


Figure 5 Connectivity tab

The connectivity tab displays the HBAs and controller ports that the server can see.

For Fibre Channel there are four possible paths because two HBAs see two Storage Center ports.

However, for iSCSI, there are a total of six connections where there are two separate IP addresses

going to three Storage Center ports. If MPIO is not installed and the volume is mapped using the

default mapping method, the server has visibility to a total of 10 paths to a volume.

In Storage Center, a volume is mapped to all available paths unless the advanced mapping button is used

to restrict mapping paths to FC only, iSCSI only, or specified HBA ports and controller ports. To restrict

mapping paths:

1. In the tree view, right-click a volume and select Map Volume to Server. The Map Volume to

Server window appears.

2. Select a server and click Continue. The Map Volume window appears.

3. Click Advanced.

4. Check Only map using specified server ports.

5. Select one of the following:

- Limit ports by transport type. Select a transport from the drop-down menu.

-or-

- Map using specific server ports. Check the specific server ports.


Figure 6 Advanced Mapping wizard

Assuming the default mapping wizard is used and paths are not restricted, a volume is mapped to all

available paths, creating multiple I/O paths from the server to the volume.

To view the mapped paths, select a volume in the tree view and click the Mapping tab.

Figure 7 Volume Mapping tab

Figure 7 shows that MPIO Volume 1 was mapped to the server with four FC ports and two iSCSI ports.


3.5 Choose the I/O transport Most organizations today have settled on either Fibre Channel or iSCSI for the I/O transport mechanism.

With the advent of 10GB iSCSI, the performance gap between these two transports has narrowed.

Choosing between these two depends on what the organization has in place today and where they are

heading in the future. Dell Compellent offers 8GB and 16GB Fibre Channel and 10GB iSCSI. For a

converged fabric iSCSI is the best option because it can utilize existing networking infrastructure.

The remainder of this document focuses on specific MPIO configuration options available from:

Windows Server 2003 Dell Compellent-provided DSM

Windows Server 2008 and above MSDSM

Microsoft iSCSI DSM

It is assumed that there are multiple front-end controller paths to the servers and that the servers have

multiple connections to the controller.


4 MPIO for Windows Server 2003 Windows Server 2003 offers two methods for handling MPIO:

Storage Center ISV-provided DSM

Microsoft iSCSI DSM

These two methods cannot be used concurrently in the Windows 2003 platform. This chapter describes

each of these options and provides guidance on how to configure MPIO with both the Storage Center

DSM and the Microsoft DSM.

4.1 Dell Compellent Multipath Manager The Dell Compellent Multipath Manager is a Dell Compellent-provided DSM that handles all Fibre Channel

and iSCSI failover and load balancing. Fibre Channel requires the Dell Compellent Multipath Manager.

iSCSI can be configured with either the Microsoft iSCSI DSM or the Dell Compellent Multipath Manager.

For information on installing and configuring the Dell Compellent Multipath Manager, refer to the Storage

Center Multipath I/O (MPIO) Manager for Microsoft Servers User Guide on the Dell Compellent Knowledge

Center.

Once the Dell Compellent DSM has been installed, configure the load balance policies for the volumes

attached to the server. The default load balance policy for the Dell Compellent DSM is failover-only.

However, this can be changed to round robin or round robin subset.

Failover only: Only one path is active. I/O fails over to the next available standby path only when the

active path fails. The new active path remains active until another failover occurs. By default, the first

discovered path is the active path. You can configure the failover only policy to behave as failback by

setting the active path and enabling the preferred path option. For failback, the system fails back to

the original active path when it becomes available after a failover.

Round robin: All paths are active and I/O is distributed across all paths.

Round robin subset. Allows multiple active and standby paths; I/O is distributed across all active

paths. Standby paths are used only when all active paths fail. The round robin subset policy can be

configured to behave as failback by explicitly setting one or more active paths. For failback, the

system fails back to the original active path when it becomes available after a failover.




4.2 Configuration To configure the default load balance policy or to change the active configuration of the DSM, open the

Dell Compellent Multipath Manager Configuration wizard from the Program Files menu. Below is a brief

overview of how to change the policies.

To change the default load balance policy for all future volumes attached to the system:

1. Click Set Default Policy at the top of the screen.

2. In the Policy field, select a policy for the environment.

To change the policy for a given device:

1. Click on the device.

2. From the drop down menu, select the desired load balance policy.

Note: If moving to a round robin policy, notice that the device paths do not change from standby to

active until the settings are applied and the wizard is restarted or refreshed.

4.3 Choosing a failover policy Determining the best failover policy is accomplished by deciding which is more important for the

application: failover, performance, or a combination of both. Cost also plays a significant role in the

decision since having multiple paths adds to the overall cost of a solution. However, in today's world of

zero downtime, failover is required in most organizations.

As mentioned previously in failover only mode, the server uses only one path at a time. While this ensures

redundancy, it may not provide adequate bandwidth for certain workloads. Also, any I/O ports in standby

mode are sitting idle until a failover occurs, resulting in underutilized resources in a data center.


Round robin, on the other hand, provides a means for I/O to traverse all available paths while still providing

a level of redundancy. If one path fails, the system uses the remaining paths to complete the request.

4.4 iSCSI multipath options As mentioned previously, the Dell Compellent Multipath Manager handles both FC and iSCSI connections.

In the Dell Compellent Configuration window, the transport for each connection can be viewed and

configured for each volume.

Figure 8 Dell Compellent DSM with both FC and iSCSI

However, if the built-in Microsoft iSCSI DSM is installed, the Dell Compellent Multipath Manager software

must be uninstalled. Typically this is done for a server with volumes connected only via the iSCSI transport.

Otherwise there is no way to control the Fibre Channel MPIO functionality. If a Windows Server 2003 is

using both transports, the best practice is to use the Dell Compellent DSM and not install the Microsoft

iSCSI DSM.

4.4.1 Installing the Microsoft iSCSI DSM To install the MS iSCSI DSM, simply install the iSCSI initiator software and select Microsoft MPIO

Multipathing Support for iSCSI.


Figure 9 Installing MS iSCSI DSM

Once installed, all iSCSI volume MPIO characteristics are controlled by the MS iSCSI DSM. Before jumping

into MPIO configuration with iSCSI it is important to understand how to connect and configure the iSCSI

initiator.

4.5 Configuring the iSCSI Initiator When using the MS DSM or the Dell Compellent DSM for iSCSI, the server must first be configured to

communicate with the Dell Compellent iSCSI front-end ports. This section describes how to configure the

iSCSI Initiator and make this connection. It assumes that the initiator software is installed, the server has

been rebooted, and the Dell Compellent Storage Center has two or more iSCSI front-end ports. In the

following examples, the server is configured with two NIC cards, each used to communicate with the

iSCSI network. To configure the connection to the Dell Compellent Storage Center:

1. Open the iSCSI Initiator.

2. Click the Discovery tab. The Discovery tab contains two sections: Target Portals and iSNS Servers.

Dell Compellent front-end ports are added as target portals.


3. Click Add. If using virtual port mode, enter the IP address of the control port. If using legacy port

mode, enter the first primary port IP address. Do not enter reserve ports. Continue until all front-

end ports have been added.

4. Click the Targets tab. In this example there are two targets. For MPIO to function correctly, each

of the NIC cards must be logged in to each target, thus providing multiple connections to a

specific target.

5. Select the first target and click Log On.

6. Check Automatically Restore to reconnect after a reboot.

7. Check Enable multi-path.

8. Click Advanced.

The advanced options window is where each NIC card is selected to connect to the target. This

log-on sequence must be done for each IP address that communicates with the front-end port. In

this example, it is entered two times for each target. Follow the steps below to make a connection

for each.

9. Select Microsoft iSCSI Initiator from the Local adapter drop-down box.

10. Select the first IP address from the Source IP.

11. Select the Target Portal.

12. Select the necessary checkboxes for Data Digest and Header Digest.

13. Enter any Chap login information and click OK.

14. Select the same target and click Log On again.

15. Repeat steps 3-11 for each Source IP and each additional target.

In this example, there are two targets and two source IP addresses. Each IP address is logged in to

each target, creating four separate connections to the controller.

To verify:

1. Open the Dell Compellent System Manager. Create a server (if it hasn't already been created).


2. Click the server in the tree view.

3. Click the Connectivity tab. The connectivity window shows the IQN of the server and associated

controller ports (target IP addresses) that the server can see.

As seen in this example, the two Dell Compellent ports see each of the server IP addresses as

being connected (10.5.25.33 and 10.5.25.40).

The iSCSI Initiator provides another method for verification:

1. From the Targets tab in the iSCSI Initiator, select each of the targets.

2. Click Details to see that there are two connections for each of the targets.

3. Click Connections to verify that each connection is using a different source IP address.

4.6 Configuring Microsoft iSCSI DSM At this point the server and the Dell Compellent Storage Center are connected and the connectivity has

been verified. The next step is to use the Microsoft iSCSI DSM to configure the default load balance policy

for any new volumes that are mapped to the server.

To configure the default MPIO policy:

1. Open the iSCSI Initiator and click the Targets tab.

2. Select each target and click Details. Within the details section, there are two or more Identifiers.


3. Select each one and click Connections.

4. Using the drop down menu, select an appropriate load balance policy for that connection, and

click Apply.

Note that this must be done for each connection.

To configure the MPIO policy for pre-existing volumes:

1. Open the iSCSI Initiator and click Targets.

2. Select each target individually.

3. Click Details and then Devices.

4. For each device, click Advanced.

5. In the Advanced window click MPIO.

6. Select the appropriate policy for each volume and then click Apply.


The Microsoft iSCSI DSM offers three additional policies that are not provided by the Dell Compellent

DSM.

Least Queue Depth: The DSM routes I/O to the path with the least number of outstanding requests.

Weighted Paths: A weight is assigned to each path. The weight indicates the relative priority of a

given path. The larger the number, the lower the priority. The DSM chooses the path with the least

weight.

Least Blocks: The DSM routes requests to the processing path with the least number of pending I/O

blocks.

Note: Dell Compellent Storage Center does not support the three additional policies provided by the

Microsoft iSCSI DSM.

In conclusion, there are two methods for handling MPIO in the Windows Server 2003 operating system. If

multiple protocols are in use on the server, the Dell Compellent Multipath Manager Software must be

used. However, if iSCSI is the only transport, the Microsoft iSCSI DSM is a valid choice.

Note: Remember that both DSMs cannot be used on the same server because this will cause issues with

the MPIO stack.


5 Using MPIO on Windows Server 2008 and 2008 R2 Windows Server 2008 and 2008 R2 have a built-in Microsoft DSM that manages all aspects of failover and

load balancing. Dell Compellent uses this DSM because it provides all the functionality required for our

customers. This also simplifies implementation, as it eliminates the need to install and maintain another

piece of software in the environment. The built-in DSM for Windows Server 2008 (and above) can manage

both iSCSI and FC volumes.

The process for mapping volumes and creating servers is identical to the process with Windows Server

2003 described in Section 3, “Configuring servers”. The rest of Section 5 covers Windows Server 2008 and

2008 R2 configuration options.

Note: Please refer to Appendix A in this document for important Windows Server 2008 and 2008 R2

MPIO configuration recommendations.

5.1 Installing the Microsoft MPIO DSM For Windows Server 2008 and above, the process of installing and configuring the Microsoft MPIO DSM

has been streamlined. A new configuration tool, the Server Manager, provides a single interface for

installing server features and roles. To access Server Manager click Start Control Panel

Administrative Tools Server Manager or click the Server Manager icon in the toolbar. There are

currently two available options for installing the DSM: the Server Manager GUI or the servermanagercmd

command line interface (CLI).

5.1.1 Server manager GUI To install using the GUI on Server 2008 and 2008 R2:

1. Open Server Manager.

2. In the tree view, click Features.

3. Check MPIO and click Next.

4. Click Install. Once the feature has been installed click Yes, if prompted, to allow the reboot.

5.1.2 Server manager CLI (2008 and 2008 R2 only) To install using the CLI, open a command prompt with elevated (administrator) privileges and type:

Servermanagercmd -install "Multipath-IO"

5.1.3 To install MPIO on Server Core: For a Windows Server 2008 Core installation, open a command prompt and type:

start ocsetup MultipathIo


For a Window Server 2008 R2 Core installation, open a command prompt and type:

DISM /online /enable-feature:MultipathIo

Note: For server core installations, the above commands are case sensitive and must be run before the

MPCLAIM command can be used.

At this point, the Microsoft MPIO DSM has been installed but not configured. Dell Compellent volumes

must be associated with the DSM so that it can manage MPIO characteristics. The Microsoft DSM manages

all Fibre Channel and iSCSI volumes presented by the Dell Compellent Storage Center. You can choose

either or both of these transports. The built-in iSCSI initiator or an iSCSI HBA can also be used with the

same management for the iSCSI Multipath I/O.

The iSCSI initiator provides all necessary performance and stability. However, Dell Compellent supports

use of an HBA.

5.2 Associating Dell Compellent volumes with the DSM This section will describe how to associate the DSM with Dell Compellent volumes and how to setup and

configure the DSM based on the failover and load balancing policies of an organization. These instructions

assume that servers have been created in the Dell Compellent System Manager and that at least one

volume is mapped to the server via FC or iSCSI with MPIO enabled.

To associate the DSM with Dell Compellent volumes:

1. Open the MPIO control panel by clicking Start Administrative Tools MPIO.

2. Once opened, click Discover Multi-Paths.

3. Under Others, COMPELNTCompellent Vol appears.

Note: If COMPELNTCompellent Vol does not appear, rescan disk devices in Disk Management. Click on

COMPELNTCompellent Vol and then click Add. This can take a minute. When Disk Management

prompts to reboot the server, accept the prompt and allow the server to reboot. This reboot is required

to set up the association between the volumes and the DSM.

Another option for providing associations is the MPCLAIM CLI command. Open a command prompt with

elevated (administrator) privileges and type the following:

mpclaim.exe -r -i -d "COMPELNTCompellent Vol"

This command provides the same result as the Control Panel option. It associates a Dell Compellent

volume and then restarts the server. To bypass the reboot option (if rebooting later is desired), use -n in

place of the -r.

Once the server reboots, use Disk Management to verify that the configuration is correct. There should

only be one instance of each SAN volume listed in Disk Management.


5.3 Setting the default load balance policy Once the volumes are associated, specify the default load balance policy and change any existing volumes

to use the new policy. There are some slight differences between Windows 2008 and Windows 2008 R2.

5.3.1 Windows Server 2008 default load balance policy By default in Windows Server 2008, the Dell Compellent volumes have a load balance policy of failover

only because a Storage Center is not an Asymmetric Logical Unit Assignment (ALUA) device. Unfortunately

with Server 2008, there is no way to change the default policy. Therefore, it is imperative that the policy is

changed to reflect the best practices of an organization each time a volume is mapped to the server.

The same procedure is used to change the policy on a per-volume basis with both Windows 2008 and

Windows 2008 R2.

5.3.2 Windows Server 2008 R2 default load balance policy With Server 2008 R2 and newer, a Storage Center is designated as a Round Robin device by default.

However, 2008 R2 and newer provides a method for changing the default policy system-wide as well as

on a per-volume basis.

To change the default load balance policy in Server 2008 R2, Server 2012 and Server 2012 R2, use the

MPCLAIM CLI command as follows:

mpclaim.exe -L -M <0-7> -d "COMPELNTCompellent Vol"

<0-7> refers to the desired load balance policy and shown in Table 1.

Table 1 Windows 2008 R2 Load Balance Policy

Parameter Definition

0 Clear the policy

1 Failover only

2 Round robin

3 Round robin with subset

4 Least queue depth

5 Weighted paths

6 Least blocks

7 Vendor specific

For example, to change all Dell Compellent volumes to a failover only policy, use the following command:

mpclaim.exe -L -M 1 -d "COMPELNTCompellent Vol"

Note: Failover Only and Round Robin are the only policies supported on Dell Compellent Storage Center.


5.4 Per-volume load balance settings Now that the default policy is set, it is important to understand how to change the policy on a per-volume

basis. Some organizations may require a different policy based on the type of application or service

provided. Use Disk Management in 2008 and 2008 R2 or through the MPCLAIM utility in 2008 R2 to

change the per-volume policy. To change the policy in Disk Management:

1. Click Start Administrative Tools Server Manager.

2. In the tree view, click Storage Disk Management.

3. Right-click the disk number in the disk column and select Properties.

4. Select the MPIO tab.

5. From the drop-down box, select the appropriate MPIO policy for the volume.


5.4.1 Using MPCLAIM in Windows Server 2008 R2, 2012 and 2012 R2 Windows Server 2008 R2, 2012 and 2012 R2 provide an enhanced MPCLAIM utility that allows the policy

to be changed on a per-volume basis much like Disk Management. The command is similar to setting the

default policy for all volumes. However, in this case the administrator chooses which volume to set.

List of all MPIO volumes on the system with the following mpclaim command:

mpclaim.exe -s –d

Figure 10 List disks with MPCLAIM

Figure 10 shows that the current policy for Disk 0 is RR (Round Robin). Use the mpclaim.exe command to

change the policy for this disk.

mpclaim.exe -L -M 1 -d 0

Refer to Microsoft TechNet for the full MPCLAIM reference guide.

http://technet.microsoft.com/en-us/library/ee619743(v=ws.10).aspx


6 MPIO for Windows Server 2012 and 2012 R2 MPIO for Windows Server 2012 and 2012 R2 functions the same way as it does for 2008 R2. However,

Server 2012/R2 includes the MPIO module in Windows PowerShell®. The MPIO module is a powerful

alternative to using the MPCLAIM command. Although the MPCLAIM command is included in Server

2012/R2, Microsoft recommends using the MPIO module in PowerShell. This chapter focuses on using

the GUI and PowerShell to install and configure MPIO.

Note: On Server Core installations, please follow the instructions for PowerShell. PowerShell can be

accessed on a Server Core installation by typing powershell and pressing [Enter] at the command

prompt.

Windows Server 2012 and 2012 R2 include the ability to use heterogeneous HBA types with MPIO. In

previous versions of Windows Server, it was a requirement to use HBAs of the same model. Like Windows

Server 2008 and 2008 R2, Windows Server 2012 and 2012 R2 contain a built-in Microsoft DSM out of the

box that manages all aspects of failover and load balancing.

Note: Please refer to Appendix A in this document for important Windows Server 2012 and 2012 R2 MPIO

configuration recommendations.

6.1 Install the Microsoft MPIO feature The MPIO DSM can be installed on Server 2012 and 2012 R2 either through the GUI or through the MPIO

module in PowerShell.

6.1.1 Server manager GUI 1. Open Server Manager.


2. From the Dashboard, click Add roles and features.

3. When the Add Roles and Features Wizard window opens, click Next.

4. Select Role-based or feature-based installation and click Next.

5. Choose the local server, and click Next.

6. Without selecting a role to install, click Next on the Select server roles screen.

7. Check Multipath I/O, and then click Next.


8. Check the box to Restart the destination server automatically if required.

9. Click Install.

10. Click Close when finished.

6.1.2 Enable MPIO with PowerShell 1. Open a PowerShell window with elevated (administrator) privileges.

2. At the PowerShell prompt, type in the following command:

Enable-WindowsOptionalFeature –online –FeatureName MultiPathIO

Figure 11 Enable MPIO in PowerShell

6.2 Associate Dell Compellent volumes with the in-box DSM Now that the DSM has been installed, Dell Compellent volumes must be associated with the DSM so that

the DSM can manage MPIO characteristics. On Windows Server 2012 and 2012 R2, Dell Compellent


volumes can be associated with the DSM through the use of either the MPIO Control Panel, or through

PowerShell.

Note: Once the DSM is associated with Dell Compellent volumes, Windows will automatically claim all

Fibre Channel and iSCSI volumes presented from Storage Center and apply default MPIO settings to

those volumes.

6.2.1 Using the MPIO control panel To associate the Dell Compellent volumes with the DSM through the use of the MPIO Control Panel,

follow these steps.

1. Open the MPIO Control Panel through Server Manager, by clicking Tools and then MPIO. MPIO

can also be accessed through the Control Panel.

2. Click on the Discover Multi-Paths tab.

3. Under Others, COMPELNTCompellent Vol should be displayed.


4. Highlight COMPLENTCompellent Vol, and click Add.

5. Click Yes on the Reboot Required window.

6. Once the server has rebooted, open up the MPIO Control Panel and verify that

COMPELNTCompellent Vol is listed under Devices on the MPIO Devices tab.


7. Click OK to close the window.

6.2.2 Using PowerShell To associate the Dell Compellent volumes with the DSM through the use of PowerShell, follow these

steps.

1. Open a PowerShell window with elevated (administrator) privileges.

- On Server Core installations, type in powershell and press [Enter] at the command prompt

2. At the PowerShell prompt type:

New-MSDSMSupportedHW –VendorID COMPELNT –ProductID ‘Compellent Vol’

3. Now that Dell Compellent is supported through the Microsoft DSM, claim all available Dell

Compellent volumes to be used by MPIO by typing:

Update-MPIOClaimedHW –Confirm:$false

4. Restart the server by typing:

shutdown –r –t 0 [Enter]


6.3 Set the Default Load-Balancing Policy Similar to Server 2008 R2, the default load balancing policy for Server 2012 and 2012 R2 is round robin.

However, the default load balancing policy can be changed system-wide or on a per-volume basis.

Storage Center supports the round robin and failover only load-balancing policies for Server 2012 and

2012 R2.

To change the default load balancing policy to failover only, open a PowerShell window with elevated

(administrator) privileges and type:

Set-MSDSMGlobalDefaultLoadBalancePolicy –Policy FOO [Enter]

Figure 12 Set default load balance policy to failover only

To change the default load balancing back to round robin, type:

Set-MSDSMGlobalDefaultLoadBalancePolicy –Policy RR [Enter]

Figure 13 Set default load balance policy to round robin

To verify the default load balance policy, type:

Get-MSDSMGlobalDefaultLoad BalancePolicy

If the default policy is set to round robin, the result will return “RR”:

Figure 14 Round robin default load balance policy

If the default policy is set to failover only, the result will return “FOO”:

Figure 15 Failover only default load balance policy


6.4 Per-volume load balance settings Changing load balance settings on specific volumes can be done through the Disk Management GUI, or

from PowerShell.

6.4.1 Using the disk management GUI: 1. Click Start Administrative Tools Computer Management.

2. In the tree view, click Storage Disk Management.

3. Right-click the desired disk number and select Properties.

4. Select the MPIO tab.

5. From the drop-down box, select the appropriate MPIO policy (Failover Only or Round Robin) for

the volume.


6.4.2 Using PowerShell The PowerShell MPIO module does not include cmdlets that can change the default load balancing policy

on a specific volume. Similar to Server 2008 R2, the MPCLAIM command must be used to make changes

to specific volumes.

Note: The load balancing policy cannot be changed from round robin to failover only using the

MPCLAIM command. MPCLAIM only supports switching from failover only to round robin.

To change the default load balancing policy on a single volume, open a command prompt or PowerShell

window with elevated (administrator) privileges (commands will work in both):

To list all MPIO volumes on the system, type :

mpclaim –s –d

Figure 16 Listing MPIO volumes

Figure 16 shows that the load balancing policy (LB Policy) is set to RR (round robin) for all three volumes.

The syntax to change the load balancing policy on a specific volume is:


mpclaim –l –d <disk #> <0-7>

Refer to Table 1 in section 5.3.2 for load balancing policies and the associated numbers for the mpclaim

command.

For example, to change the load balancing policy of MPIO disk 2 to round robin, type:

mpclaim –l –d 2 2 [Enter]

Figure 17 Set load balancing setting

Verify the new settings by typing:

mpclaim –s –d

Figure 18 Verifying MPIO settings


7 Configure a Windows 2008 R2, 2012 and 2012 R2 Server

for iSCSI MPIO Windows Server 2008 R2, 2012 and 2012 R2 support MPIO with the iSCSI software initiator. iSCSI initiator

software is provided natively by the Windows Server OS.

The iSCSI quick connect feature works well for single iSCSI path connectivity. Configuring iSCSI to use

MPIO requires a few more steps, but is still easy to configure.

Figure 19 iSCSI virtual ports and domains

Figure 19 represents a dual-controller Dell Compellent Storage Center that is configured with virtual front-

end ports with 2 fault domains. Two physical iSCSI ports (one from each controller) are grouped logically

as a virtual domain that is assigned a virtual iSCSI IP address. Each virtual domain’s physical ports are

connected to two separate iSCSI switches to ensure full path redundancy to the dual iSCSI NICs on the

server.


7.1 Configuration The environment created for this configuration includes (refer to Figure 19):

Windows Server 2008 R2, 2012, or 2012 R2.

Two dedicated NIC ports (one for each fault domain) on the server for iSCSI communications.

A Dell Compellent Storage Center with dual controllers configured with virtual front-end iSCSI ports

and two virtual fault domains.

The MPIO feature installed on the server.

To configure the Server for iSCSI MPIO, complete the following steps.

1. Configure two physical NIC ports on the server to use iSCSI.

a. Configure one NIC (along with the necessary cabling and switching configurations) to access

one virtual iSCSI domain, and configure the second NIC to access the other virtual iSCSI

domain.

b. In the example shown in Figure 19, the server NICs are assigned with IPs of 10.10.95.101 (for

fault domain 100), and 10.10.128.101 (for fault domain 200).

c. Once configured, the server should be able to ping both of the virtual iSCSI IP addresses

associated with the two fault domains on the Dell Compellent Storage Center. In this example,

10.10.95.1 (fault domain 100) and 10.10.128.1 (fault domain 200).

2. Log on to the Windows server and launch the iSCSI Initiator software.

a. For Server 2008 R2, go to Start Administrative Tools iSCSI Initiator.

b. For Server 2012 and 2012 R2, start Server Manager, and from the Dashboard, click on Tools

iSCSI Initiator from the drop-down list.

Note: If receiving a prompt to start the iSCSI service (for Server 2008 R2, 2012 or 2012 R2), click

Yes.

3. Select the Discovery tab, and then click the Discover Portal button.

4. Enter the IP address of the first iSCSI target IP. In this example, the virtual iSCSI IP address

associated with the first virtual fault domain on the Dell Compellent Storage Center, and then click

Advanced.


5. From the Local adapter drop-down list, select Microsoft iSCSI Initiator.

6. From the Initiator IP drop-down list, select the local IP address of the server NIC that is to be

associated with the first fault domain (fault domain 100).

This example uses Initiator IP 10.10.95.101.

7. Click OK, and then OK again to return to the iSCSI Initiator properties window.

8. Verify that the target IP address and adapter IP address are displayed in the Target Portals window.

9. Repeat steps 3 – 8 to add the second target IP for the second virtual fault domain and the server

second iSCSI NIC (in this example, 10.10.128.1 and 10.10.128.101).

10. When completed, both pairs of iSCSI initiators and targets should be listed.


11. Select the Targets tab. This should be populated with the discovered iSCSI target ports on the Dell

Compellent Storage Center.

12. Highlight the first target, and then click Connect.

13. On the Connect To Target screen, verify that both Add this connection to the list of Favorite

Targets and Enable multi-path are checked.

14. Click Advanced to display additional options.


15. Set Local adapter to Microsoft iSCSI Initiator.

16. Select the correct IP addresses for the Target portal IP and Initiator IP from the drop-down lists.

17. Click OK, and then OK again to return to the iSCSI Initiator properties window.

18. Repeat steps 12-17 above for each additional target listed.

19. When finished, all the targets should show as Connected as shown below.

20. Click OK to exit the iSCSI Initiator properties window.


A Windows Server MPIO configuration recommendations for

Dell Compellent Storage Center

Table 2 Recommended MPIO hotfix for Windows Server 2008 R2/SP1

KB Number Title Link

KB2871163 No warning logged when the Storport miniport driver tries to use more than 8 SCSI buses in Windows Server 2008 R2 (storport.sys – 7/13/2013)

http://support.microsoft.com/kb/2871163

KB2851144 Computer loses track of LUNs after a path failover occurs between storage controllers in Windows Server 2008 R2 or Windows Server 2012 (msdsm.sys – 6/1/2013)


KB2754704 A hotfix is available that provides a mechanism for DSM to notify MPIO that a particular path is back to online in Windows Server 2008 and Windows Server 2008 R2 (mpio.sys – 11/30/12)


KB2684681 Iscsicpl.exe process stops responding when you try to reconnect a storage device to a computer that is running Windows Vista, Windows Server 2008, Windows 7, or Windows Server 2008 R2 (msiscsi.sys – 3/9/2012)


Table 3 Recommended MPIO hotfixes for Windows Server 2012 (non R2 version)

KB Number Title Link

KB2867201 Stop Error 0x00000050 occurs when new StorPort features are implemented in Windows 8 or Windows Server 2012 (storport.sys – 6/29/2013)


KB2889784 Windows RT, Windows 8, and Windows Server update rollup: November 2013









(msdsm.sys – 10/04/2013)

KB2869606 The LUN for a storage device is lost when multiple paths are lost concurrently in Windows Server 2012 (mpio.sys – 10/12/2013)


KB2779768 Windows 8 and Windows Server 2012 update rollup: December 2012 (msiscsi.sys – 11/6/2012)





Note: All recommended registry settings apply to Windows Server 2008 R2, 2012, and 2012 R2.

Note: The maximum time allowed for Storage Center controller failover is 60 seconds. The value of

PDORemovePeriod directly correlates to this value, and thus, should never be set below 60 seconds. In

most cases, the recommended value of 90 seconds will be sufficient. In environments with failover

clusters that require faster failover times, a value of 60 can be used. System administrators are advised to

test settings on a non-production environment to make informed decisions on setting timeout values.

Table 4 Recommended MPIO Registry Settings

Location: HKLM\System\CurrentControlSet\Services\mpio\Parameters

Setting Name Description MSFT Default Value

Recommended CML Value

PDORemovePeriod This setting controls the number of seconds that the multipath pseudo-LUN remains in system memory, even after losing all paths to the device. When this timer value is exceeded, pending I/O operations will be failed, and the failure is exposed to the application rather than attempting to continue to recover active paths. The maximum time allowed is MAXULONG (49,000 days).

20 120

PathRecoveryInterval Represents the period after which PathRecovery is attempted. This setting is only used if it is not set to 0 and UseCustomPathRecoveryInterval is set to 1.

0 60

UseCustomPathRecoveryInterval If this key exists and is set to 1, it allows the use of PathRecoveryInterval.

0 1

PathVerifyEnabled This flag enables path verification by MPIO on all paths every N seconds (where N depends on the value set in PathVerificationPeriod). This Boolean function must be filled with either 0 (disable) or 1 (enable). By default, it is disabled.

0 no change




PathVerificationPeriod This setting is used to indicate the number of seconds with which MPIO has been requested to perform path verification. This field is only honored if PathVerifyEnabled is TRUE. This timer is specified in seconds. The default is 30 seconds. The maximum allowed is MAXULONG.

30 no change

RetryCount This setting specifies the number of times a failed I/O if the DSM determines that a failing request must be retried. This is invoked when DsmInterpretError() returns Retry = TRUE. The default setting is 3.

3 no change

RetryInterval This setting specifies the interval of time (in seconds) after which a failed request is retried (after the DSM has decided so, and assuming that the I/O has been retried a fewer number of times than RetryCount). This value is specified in seconds. The default is 1 second.

1 no change


Table 5 Recommended Disk Registry Settings

Location: HKLM\SYSTEM\CurrentControlSet\Services\Disk



TimeoutValue Disk time-out is a registry setting that defines the time that Windows will wait for a hard disk to respond to a command. Installing host bus adapters (HBA) or other storage controllers can cause this key to be created and configured.

60 no change

Table 6 Recommended iSCSI Initiator Registry Settings

Location: HKLM\SYSTEM\CurrentControlSet\Control\Class\{4D36E97B-E325-11CE-BFC1-

08002BE10318}\<Instance Number>\Parameters



MaxRequestHoldTime Maximum number of seconds that requests are queued if connection to the target is lost and the connection is being retried. After this hold period, requests will be failed with "error no device" and device (disk) will be removed from the system.

60 90

LinkDownTime This value determines how long requests will be held in the device queue and retried if the connection to the target is lost. If MPIO is installed this value is used. If MPIO is not installed MaxRequestHoldTime is used instead.

15 35

TCPConnectTime Timeout given to TCP when a Connect request is sent.

15 no change

TCPDisconnectTime Timeout given to TCP when a Disconnect request is sent.

15 no change

WMIRequestTimeout Timeout value set for WMI requests such as LoginToTarget, LogoutFromTarget, SendTargets, etc.

30 no change




DelayBetweenReconnect If a connection is dropped while it is in FullFeature phase, the driver will attempt to re-login. This parameter sets the delay between each re-login attempts.

1 no change

MaxConnectionRetries Maximum number of times a lost TCP connection will be retried.

-1 (indefinitely) no change

MaxPendingRequests This setting controls the maximum number of outstanding requests allowed by the initiator. At most this many requests will be sent to the target before receiving response for any of the requests.

255 no change

EnableNOPOut If set to 1, the initiator will send NOP OUT PDUs to target if there is no activity for 2 minutes.

0 1

MaxTransferLength This is maximum data size of an I/O request.

262144 (256KB)

no change

MaxBurstLength This is the negotiated Max Burst Length.

262144 (256KB)

no change

FirstBurstLength This is the negotiated First Burst Length.

65536 (64KB) no change

MaxRecvDataSegmentLength This is the negotiated MaxRecvDataSegmentLength.

65536 (64KB) no change

IPSecConfigTimeout Timeout value used when the driver calls the discovery service to configure\release IPsec for an iSCSI connection.

15 no change

InitialR2T If set to Non-Zero value, initiator will request InitialR2T (InitialR2T=Yes). Else initiator will not request InitialR2T (InitialR2T=No).

0 no change




ImmediateData If set to Non-Zero value, initiator will request ImmediateData (ImmediateData=Yes). Else initiator will not request ImmediateData (ImmediateData=No).

1 (Yes) no change

PortalRetryCount This value is used to determine how many times a connect request to a target portal should be retried if the portal is down.

1 no change

NetworkReadyRetryCount This value is used to determine how many times initiator should retry getting the IP address of NIC corresponding to the PortNumber specified in the login request.

10 no change

ErrorRecoveryLevel Error recovery level that the initiator will request.

2 no change

AsyncLogoutPauseTimeout This is the number of seconds that the initiator pauses the I/O queue after receiving an async logout.

10 no change

Note: A reboot is required for the change to take effect. Alternatively, unloading and reloading the

initiator driver will also cause the change to take effect. In the Device Manager GUI, look under SCSI and

RAID Controllers. Right click Microsoft iSCSI Initiator and select Disable to unload the driver. Then

select Enable to reload the driver.

Sources:

Microsoft iSCSI Initiator Documentation (March 2012) - Link

Configuring MPIO Timers (September 2009) - Link

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=3&ved=0CFAQFjAC&url=http%3A%2F%2Fdownload.microsoft.com%2Fdownload%2FE%2F7%2FE%2FE7E6F4B0-CF58-4DA3-8547-79AD71D6DC4B%2FiSCSI%2520Initiator%2520User's%2520Guide%2520for%2520Windows%25207.docx&ei=lVk_UbDOG5KGyQHlmICYAQ&usg=AFQjCNGt2Xg8PYW_o8jt3D5-k_gxF9CKhw&sig2=xVg6HK4-fy3oNB-Bz55dPQ&bvm=bv.43287494,d.aWc



B Additional resources

Support.dell.com is focused on meeting your needs with proven services and support.

DellTechCenter.com is an IT Community where you can connect with Dell Customers and Dell employees

for the purpose of sharing knowledge, best practices, and information about Dell products and

installations.

Referenced or recommended Dell Compellent publications on Knowledge Center:

http://kc.compellent.com

Dell Compellent Storage Center MPIO Users Guide

Dell Compellent Storage Center Connectivity Guide

Dell Compellent Storage Center Multipath IO (MPIO) Manager for Microsoft Servers User Guide

Dell Compellent Storage Center Windows Server 2012/R2 Best Practices Guide

Referenced or recommended Microsoft publications:

Microsoft MPIO Step-by-Step Guide (2008 R2)


Configuring iSCSI MPIO on Windows Server 2008 R2

http://blogs.technet.com/b/migreene/archive/2009/08/29/3277914.aspx

Microsoft MPIO Users Guide for Windows Server 2012

http://www.microsoft.com/en-us/download/details.aspx?id=30450

MPCLAIM Reference Guide


Managing MPIO with Windows PowerShell on Windows Server 2012

http://blogs.msdn.com/b/san/archive/2012/07/20/managing-mpio-with-windows-powershell-

on-windows-server-2012.aspx

Multipath I/O (MPIO) Cmdlets in Windows PowerShell Reference

http://technet.microsoft.com/library/hh826113.aspxhttp://msdn.microsoft.com/en-

us/library/dd758814.aspx



http://blogs.technet.com/b/migreene/archive/2009/08/29/3277914.aspx

http://www.microsoft.com/en-us/download/details.aspx?id=30450


http://blogs.msdn.com/b/san/archive/2012/07/20/managing-mpio-with-windows-powershell-on-windows-server-2012.aspx

http://blogs.msdn.com/b/san/archive/2012/07/20/managing-mpio-with-windows-powershell-on-windows-server-2012.aspx

http://technet.microsoft.com/library/hh826113.aspx

http://technet.microsoft.com/library/hh826113.aspx

http://msdn.microsoft.com/en-us/library/dd758814.aspx

CML1004-Microsoft MPIO Best Practices

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