Whitepaper Server Virtualisation And Storage Management

Server

Virtualisation

And

Storage

Management

Optimising Storage Management to Obtain

Greater Benefits from Server Virtualisation

Alan McSweeney

ServerVirtualisation and Storage Management

Contents Server Virtualisation........................................................................................3 Server Virtualisation Architecture....................................................................4 Configuration ...............................................................................................4 Virtual Server Resilience ..............................................................................4 Virtual Server Data Backup and Recovery ...................................................5

Storage Management and Server Virtualisation................................................6 Virtual Server Backup and Recovery............................................................8 IBM N Series SnapMirror .............................................................................9 IBM N Series FlexVol and FlexClone............................................................9 IBM N Series RAID Double Parity ..............................................................9 Conclusion.................................................................................................. 10

Server Virtualisation and Storage Management

Server Virtualisation Implementing server virtualisation (using software such as VMware) can deliver substantial benefits to IT and business by reducing the number of deployed Intel-based servers by 50% or more while delivering benefits such as:

• Improved server utilisation rates - 60% to 80% (up from typical rates of less than 15%)

• Server and application provisioning time measured in hours not days

• Reduction in downtime such as hardware maintenance

• Reduction in operating costs

• Increased server and application resilience

• Simplification of server operation and administration

• Increased levels of service Implementing server virtualisation also provides a platform for:

• Facilitating business continuity and disaster recovery

• Improved backup and recovery A little additional planning and investment will deliver significant additional benefits for a virtualised server environment in terms of:

• Faster backup and recovery

• Protection against application corruption

• Improved business continuity and disaster recovery Implementing server virtualisation requires some form of shared storage to enable features such as HA (High Availability) and DRS (Dynamic Resource Scheduling). In order to implement an effective, efficient, resilient and performing virtualised server infrastructure, the storage component needs to be designed correctly. This can include taking advantage of features in a virtualised server infrastructure such as snapshotting and virtual backup. This whitepaper discusses some of the issues regarding the configuration of storage for server virtualisation to derive a more complete set of benefits. This whitepaper makes reference to one storage subsystem from NetApp and also sold by IBM as the N Series.

Once confined to server rooms, virtualization has now made it into the mainstream of computing. And by 2010, virtualization will be the single most important technology for IT departments, according to research firm Gartner.


Server Virtualisation Architecture

Configuration Optimising the benefits of server virtualisation will involve implementing a virtualisation infrastructure along the following lines:

There will be two (or more) sets of physical servers onto which servers are virtualised. These can be configured to operate as active/active or active/passive. The physical servers will be connected to shared storage such as a fibre-channel or iSCSI SAN. The I/O load that was distributed across a large number of separate physical servers is now concentrated onto a smaller number of servers hosting the virtual servers.

Virtual Server Resilience A configuration such as this provides multiple points of resilience

• 80% of businesses have no plan

o “It won’t happen to me”

• 68% of businesses who experience a disaster and don’t have a plan go out of business within 2 years

• One in five organisations will suffer a major IT disaster in five years

• A company experiencing a computer outage lasting longer than 10 days will never fully recover


In the event of the failure of a physical server within the virtual infrastructure the virtual servers can be restarted on either another server within the same infrastructure or to a server on the other infrastructure.

Virtual Server Data Backup and Recovery There are two options for backing-up virtual servers within a virtual infrastructure using software-based backups: 1. The existing process for backing-up physical servers can be implemented in

the virtual environment – backup agents for your existing backup tool can be installed on the virtual servers and these servers backed-up as normal.

2. Using VCB (Virtual Consolidated Backup) to capture server images – the entire virtual server can be backed-up to a separate Proxy Server that can then backup the images using existing backup software. A backup agent for your existing backup software is installed on the VCB server. This reduces backup software costs but decreases the granularity of what can be recovered.

Standard Server Backup Virtual Consolidated Backup


Storage Management and Server Virtualisation In a virtualised server environment, storage and its management assumes a greater importance that for normal server configurations:

• Shared storage in the form of a SAN is required to take advantage of advanced virtualisation features such as HA (High Availability) and DRS (Dynamic Resource Scheduling)

• All virtual server I/O will be concentrated onto the SAN

• A resilient storage subsystem will be required to ensure that the availability of the virtual server environment.

The IBM N Series storage subsystem provides hardware and software that provides significant advantages when used in a virtualised server environment:

• IBM N Series FlexVol technology enables you to create multiple flexible volumes on a large pool of disks, aggregate I/O across all physical disks on NFS, iSCSI or Fibre Channel. You can dynamically allocate storage and add storage capacity as needed without downtime.

• IBM N Series FlexClone provides instant clones of VMs without impacting server resources and requiring additional storage capacity. This allows you to take copies of production virtual servers for testing, validation and development


• IBM N Series Snapshot allows VMware users to make fast and space-efficient backup copies of active data with negligible performance and storage overhead.

• IBM N Series SnapMirror protects data and accelerates recovery, by providing a simple, efficient way to replicate data between systems in multiple locations using multi-transport (IP and FC) and frequency choice (synchronous, semi-synchronous, and asynchronous) options while only transferring changed blocks.

• IBM N Series Raid-DP (Double Parity) offers significantly more protection than single parity schemes (including RAID 5 and RAID 4), with zero to minimal cost and performance impact. Compared to RAID 1 (mirroring), RAID-DP offers equivalent data protection against double disk failure at a fraction of the cost of mirroring. Compared to RAID 6, RAID-DP offers better performance and ease of use.

The IBM N Series storage system provides a unified storage solution that incorporates data management, snapshots, real-time backup and disk-to-disk server backup. This simplifies the management of the vital storage component of a virtual infrastructure. The IBM N Series is ideally suited to a virtual server environment.

Of those companies participating in the 2001 Cost of Downtime Survey:

• 46% said each hour of downtime would cost their companies up to $50k

• 28% said each hour would cost between $51K and $250K

• 18% said each hour would cost between $251K and $1 million

• 8% said it would cost their companies more than $1million per hour.


Virtual Server Backup and Recovery Backing-up and ensuring that the backups are recoverable for large numbers of virtual servers can be a difficult task. The task can be more difficult because of the need to ensure that backup I/O does not affect production I/O resources. Multiple modes of backup – mirroring, point in time snapshots, offsite point in time snapshots – can be extended to all virtual servers and ensure recovery.

Existing Server Backup IBM N Series Comprehensive Server Backup Model

Using the IBM N Series in a virtual server environment enables you to implement a variety of backup and recovery approaches and techniques across the entire virtual infrastructure seamlessly using one common interface and tool. Because backups are disk-based, they are directly recoverable. IBM N Series Snapshots do not result in any data movement and have any impact on I/O, unlike the type of Snapshots available for other storage systems. Therefore they are ideally suited for use in a virtual server environment. Industry Standard Snapshot Model IBM N Series Snapshot Model

SnapVault software can be used to move SnapShots to a separate storage location to act as a disk-to-disk backup. Snapshots can be restored using SnapRestore software. The N Series solution can support thousands of snapshots. Unlike other storage subsystems, the N Series does not suffer any performance degradation. The

At what point is the survival of your company at risk?

• 40% said 72 hours



• 8% said 8 hours 9% said 4 hours

• 3% said 1 hour

• 4% said within the hour

Cost of Downtime Survey Results, 2001


performance impact of snapshots using other hardware platforms can involve a 60% or greater reduction in I/O performance. With the IBM N Series, multiple separate snapshot schedules or policies can be maintained, such as hourly snapshots retained for several days, daily snapshots retained for several weeks, weekly snapshots retained for several months and so on.

IBM N Series SnapMirror SnapMirror provides simple, flexible, and cost-effective replication software for disaster recovery and data distribution. SnapMirror can replicate virtual servers from one virtual infrastructure to another to facilitate very rapid recovery and business continuity. Exceptionally powerful, yet easy to implement and manage, IBM N Series SnapMirror software combines disaster recovery and data distribution in a streamlined solution that supports today's global enterprises. SnapMirror is a very cost-effective solution with efficient storage and network bandwidth utilisation, and provides additional value by enabling you to put the DR site to active business use. SnapMirror offers a straightforward set-up that you can easily replicate across all your IBM N Series storage systems. Once installed, SnapMirror requires minimal management, and SnapManager software ensures effortless replication of application-consistent snapshots. SnapMirror can mirror data from FC storage to ATA storage, reducing storage costs. To reduce network usage, SnapMirror works with Snapshots to send only changed data blocks to the disaster recovery storage. SnapMirror enables space-efficient copies to be created on the disaster recovery storage for other uses such as testing, development, and quality assurance, without affecting the production system. SnapMirror also enables centralised backup of data to tape from multiple data centres, reducing investment in tape infrastructure as well as offloading the production system from tape backups.

IBM N Series FlexVol and FlexClone FlexVol volumes are virtual dynamic storage entities that can grow and shrink without being constrained by the underlying physical storage. FlexClone uses ShapShot technology to create writable clones of FlexVol volumes. Clones can be created nearly instantaneously and with little I/O and storage overhead. FlexClone technology can be used to create copies of production systems for testing, validation and development.

IBM N Series RAID Double Parity IBM Storage System N series introduces double-parity RAID, named RAID-DP. This section provides an overview of RAID-DP and how it dramatically increases data fault tolerance from various disk failure scenarios. Other key


areas covered include how much RAID-DP costs, special hardware requirements, and converting from existing RAID4-based volumes to RAID-DP. This document presents a double-disk failure recovery scenario to show how RAID-DP both allows the volume to continue serving data and recreates data lost on the two failed disks. Traditional single-parity RAID offers adequate protection against a single event, which could be either a complete disk failure or a bit error during a read. In either event, data is recreated using both parity and data remaining on unaffected disks in the array or volume. If the event is a read error, then recreating data happens almost instantaneously, and the array or volume remains in an online mode. However, if a disk fails, then all data lost on it has to be recreated, and the array or volume will remain in a vulnerable degraded mode until data has been reconstructed onto a spare disk. It is in degraded mode that traditional single-parity RAID shows its protection capabilities have not kept up with modern disk architectures. RAID Double Parity significantly increases the fault tolerance from failed disk drives over traditional RAID. IBM System Storage N series uses a new type of RAID protection named RAID-DP. RAID-DP stands for RAID Double Parity, and it significantly increases the fault tolerance from failed disk drives over traditional RAID. When all relevant numbers are plugged into the standard mean time to data loss (MTTDL) formula for RAID-DP versus single-parity RAID, RAID-DP is more reliable on the same underlying disk drives. With this reliability, RAID-DP approaches RAID1 mirroring for fault tolerance, but at RAID4 pricing. RAID-DP offers businesses the most compelling total cost of ownership storage option without putting their data at an increased risk.

Conclusion An effective storage platform is essential to the successful implementation and operation of a virtualised server infrastructure. Server virtualisation requires high-performing central storage. With virtualised servers data is moved from local to central storage. The design and operation of the storage component becomes of critical importance. This is particularly true for organisations wishing to take advantage of high availability, centralised backup and business continuity and disaster recovery features of server virtualisation. IBM storage is ideally suited for use in a virtualised server environment because High Performance IBM storage solutions offer consistent high performance

with no performance degradation when taking system snapshot.

Instantaneous Backups With Snapshot technology, you can make instantaneous,

consistent backup copies of active data with negligible Streamline Storage Allocation to Virtual Machines

VMware administrators can supply storage to virtual machines in seconds while achieving the highest level of storage utilisation.


Thin Provisioning IBM storage systems offer powerful, flexible provisioning capabilities that give IT storage specialists the ability to lower cost while meeting capacity, utilisation, and performance requirements.

Raid-DP RAID-DP offers significantly more protection than single

parity schemes (including RAID 5 and RAID 4), with zero to minimal cost and performance impact. Compared to RAID 1 (mirroring), RAID-DP offers equivalent data protection against double disk failure at a fraction of the cost of mirroring. Compared to RAID 6, RAID-DP offers better performance and ease of use.

Disaster Recovery You can protect data and speed recovery using SnapMirror.

SnapMirror provides a simple, efficient way to replicate data between systems in multiple locations using multi-transport (IP and FC) and frequency choice (sync, semi-sync, and async) options while transferring only changed blocks. In the event of a disaster, a remote site can use the SnapMirror copy of the data to restart critical virtual servers with minimal disruption to ongoing operations.

Flexibility IBM storage solutions give you the ultimate in flexibility by

enabling you to choose iSCSI, FCP, or NFS connectivity within a single storage platform. IBM systems can also mix drive types within a single system so that you can tier your virtual machines (VMs) within a single architecture, giving users flexibility and investment protection.

Efficient Cloning of VMs

Using the FlexClone tool, you can instantly create VMs without consuming any additional physical storage. These clones can be used for production and test and development environments.


For more information, please contact:

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Whitepaper Server Virtualisation And Storage Management

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