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iSCSIInternet Small Computer System

Interface

BySayali Koranne

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AgendaSCSIIntroduction to iSCSIBasics of iSCSIHow it WorksArchitectureiSCSI ProtocolOpen-iSCSI : iscsid and iscsiadm utilityiSCSI InitiatorSteps for Discovery and Connect to iSCSI TargetConclusion

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SCSI :Family of Interfaces for requesting services from I/O

devices

Logical unit- Individual I/O devices

Uses Logical Addressing of data blocks

Two Types : Parallel SCSISerial SCSI

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Introduction to iSCSI :IP based standard for linking data storage devices over a network

Supports Gigabit Ethernet Interface

Enables location independent data storage and retrieval

Uses existing building blocks (SCSI, TCP)

Point to point direct connections

Transfer SCSI packets

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Basics of iSCSI:Two types of Devices:

• iSCSI Initiator• iSCSI Target

iSCSI Initiator:• Request Commands to execute

• Also called as Client

• Starts the Communication

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Cont…iSCSI Target:

Responds to the requestAlso Called as ServerIt is device that carry out commandsEndpoint within target executes command called

as Logical Unit.

CDB (Command Descriptor Block)

Task – command or linked set of command

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Cont…SCSI Command execution results in :

• Data Phase• Status Phase

SCSI driver – build SCSI CDB from request issued by application

CDB format:

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How it works:At Initiator:

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Cont…At Target:

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Architecture:

SCSI Block CommandsSCSI Stream

Commands

Parallel SCSI Transport

SCSI Applications (File Systems, Databases)

Parallel SCSI

InterfacesFibre Channel Ethernet, PPP, HDLC…

Other SCSI Commands

IP

TCP

SCSI Commands, Data, and Status

FCPSCSI over FC

iSCSISCSI over TCP/IP

Physical layer

SCSI Transport layer

SCSI Generic layer

SCSI Device layer

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iSCSI Protocol:Based on SCSIEnables block storage application over TCP/IP networksIt is bi-directionalMonitors and validates I/O operation

IP Packet

IP TCPTCP iSCSIiSCSI SCSI Data

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iSCSI address & naming conventionsiSCSI implements a client-server model

Network Entity(ISCSI client)

ISCSI node(Initiator)

Network portal IP address TCP Port #

Network Entity(ISCSI server)

ISCSI node(Target)

Network Portal IP Address TCP Port #

ISCSI node(Target)

Network Portal IP Address TCP Port #

IP network

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Cont…Initiator and target require iSCSI namesName is location independentiSCSI node name = SCSI device name Up to 255-byte displayable/human readable string

(UTF-8 encoding)Two iSCSI name types:

iqn—iSCSI qualified nameeui—Extended Unique Identifier (IEEE EUI-64—

also used for FC WWNs)

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Cont…Unique String

iqn.1987-05.com.cisco.1234abcdef987601267da232.bettyiqn.2001-04.com.acme.storage.tape.sys1.xyz

Type DateOrganization

Naming AuthoritySubgroup Naming Authority or

String Defined by Organization Naming Authorityiqn

eui

Date = yyyy-mm When Domain

Acquired

Reversed Domain Name

Type EUI-64 Identifier (ASCII Encoded Hexadecimal)

eui.02004567a425678d

Type

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Open-iSCSI: iscsid & iscsiadm utilityOpen-iSCSI is:

High-performanceTransport independentMulti-platform implementation

It is partitioned into:Kernel spaceUser Space

Kernel part implements iSCSI data path ie. iSCSI read & iSCSI write.

User space contains entire control plane.

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Cont…Open-iSCSI daemon (iscsid):

It exist in user space. Implements control path of iSCSI protocol.Daemon could be configured to automatically restart

discovery at startup.

To auto restart recovery make changes into iscsid.conf file.In iscsid –

Uncomment node.startup=automaticComment out node.startup=manual

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Cont…Open-iSCSI management utility (iscsiadm):

Is a command line tool

Usage of iscsiadm: iscsiadm [OPTION]

-m, --mode <op>

Example: -m discoverydb --type=[type] --interface=[iface...] --

portal=[ip:port]

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iSCSI Initiator:Functions as iSCSI Client

Two types of Initiator:Software Initiator

Uses code to implement iSCSI.Hardware Initiator

Uses dedicated hardware in combination with software to implement iSCSI.

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iSCSI Discovery:

iSCSI Discovery is performed in different ways:Internet Storage Name Service (iSNS) - Potential targets are

discovered by interacting with one or more iSNS servers.SendTargets – Potential targets are discovered by using a

discovery-address.SLP - Discover targets via Service Location protocol (RFC

4018) Static – Static target address is specified.

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Cont…iscsid has to be running.

Command:# Iscsiadm -m discovery -t sendtargets -p <portalip>

Example:iscsiadm -m discoverydb -t st -p somehost --discover

iscsiadm -m discovery -t st -p 192.168.1.1:3260

--discover

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Cont…Connecting to Target:

Login to Available target:# iscsiadm -m node -L all

Login to Specific target:# iscsiadm -m node --

targetname=<targetname> --login

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Conclusion:• iSCSI is a low cost, low maintenance alternative to Fibre

Channel.

• iSCSI networks can use existing copper infrastructures.

• Unlike Fibre Channel, iSCSI networks can span the Internet.

• iSCSSI works over a long distance.

• It reduces total cost storage.

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References:http://www.webopedia.com/TERM/I/iSCSI.htmlhttp://iscsi.starwindsoftware.com/why-iscsihttp://searchstorage.techtarget.com/definition/iSCSIhttp://en.wikipedia.org/wiki/ISCSIhttp://www.open-iscsi.org/docs/READMEWhite Paper :

iSCSI Protocol Concepts and ImplementationiSCSI technical white paper by Nishan systems.

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Thank You!!!

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Any Queries???