iSCSI Internet Small Computer System Interface By Sayali Koranne 05/25/2022 1
Jun 10, 2015
04/13/2023 1
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???