The document provides a detailed overview of the Internet Small Computer Systems Interface (iSCSI), which is an IP-based standard for linking data storage devices over a network. It outlines the components of iSCSI, including initiators and targets, discusses the architecture and protocol details, and explains utility tools like open-iscsi and iscsiadm for managing iSCSI connections. Ultimately, it concludes that iSCSI is a cost-effective alternative to Fibre Channel technology, enabling long-distance data storage across existing network infrastructures.

1. By
Sayali Koranne
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2. Agenda
 SCSI
 Introduction to iSCSI
 Basics of iSCSI
 How it Works
 Architecture
 iSCSI Protocol
 Open-iSCSI : iscsid and iscsiadm utility
 iSCSI Initiator
 Steps for Discovery and Connect to iSCSI Target
 Conclusion
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3. 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 SCSI
 Serial SCSI
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4. 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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5. 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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6. Cont…
 iSCSI Target:
 Responds to the request
 Also Called as Server
 It is device that carry out commands
 Endpoint within target executes command called
as Logical Unit.
 CDB (Command Descriptor Block)
 Task – command or linked set of command
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7. 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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8. How it works:
 At Initiator:
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9. Cont…
 At Target:
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10. Architecture:
SCSI Block Commands
SCSI Stream
Commands
Parallel
SCSI Transport
SCSI Applications (File Systems, Databases)
Parallel SCSI
Interfaces
Fibre Channel Ethernet, PPP, HDLC…
Other SCSI Commands
IP
TCP
SCSI Commands, Data, and Status
FCP
SCSI over FC
iSCSI
SCSI over TCP/IP
Physical layer
SCSI
Transport
layer
SCSI Generic
layer
SCSI Device
layer
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11. iSCSI Protocol:
 Based on SCSI
 Enables block storage application over TCP/IP networks
 It is bi-directional
 Monitors and validates I/O operation
 IP Packet
IP TCP iSCSI SCSI Data
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12. iSCSI address & naming
conventions
 iSCSI 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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13. Cont…
 Initiator and target require iSCSI names
 Name is location independent
 iSCSI node name = SCSI device name
 Up to 255-byte displayable/human readable string
(UTF-8 encoding)
 Two iSCSI name types:
 iqn—iSCSI qualified name
 eui—Extended Unique Identifier (IEEE EUI-64—
also used for FC WWNs)
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14. Cont…
Unique String
iqn.1987-05.com.cisco.1234abcdef987601267da232.betty
iqn.2001-04.com.acme.storage.tape.sys1.xyz
Type Date
Organization
Naming Authority
Subgroup 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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15. Open-iSCSI: iscsid & iscsiadm utility
 Open-iSCSI is:
 High-performance
 Transport independent
 Multi-platform implementation
 It is partitioned into:
 Kernel space
 User Space
 Kernel part implements iSCSI data path ie. iSCSI read & iSCSI
write.
 User space contains entire control plane.
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16. 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=automatic
 Comment out node.startup=manual
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17. 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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18. 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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19. 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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20. 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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21. 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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22. 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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23. References:
 http://www.webopedia.com/TERM/I/iSCSI.html
 http://iscsi.starwindsoftware.com/why-iscsi
 http://searchstorage.techtarget.com/definition/iSCSI
 http://en.wikipedia.org/wiki/ISCSI
 http://www.open-iscsi.org/docs/README
 White Paper :
 iSCSI Protocol Concepts and Implementation
 iSCSI technical white paper by Nishan systems.
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24. Thank You!!!
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25. Any Queries???
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