iSCSI allows SCSI commands to be sent over IP networks, extending storage networks beyond local LANs. It uses standard IP networking and requires less expertise than Fibre Channel. Key benefits include low cost by using existing network infrastructure, excellent performance as a cheaper alternative to Fibre Channel, no distance limitations, interoperability, and security features. iSCSI is recommended for budget-constrained or geographically distributed organizations and those using server virtualization.

1. iSCSI
Internet Small Computer System Interface

2. iSCSI
• iSCSI is a TCP/IP based protocol for sending
SCSI commands over IP based networks.
• This allows iSCSI infrastructure to extend
beyond a local LAN, and be used on a WAN or
even over the internet.

3. iSCSI

4. Benefits
• Low cost – iSCSI uses the existing network
infrastructure so there is no need to buy
expensive equipment.
• Easy installation and maintenance of iSCSI
SANs – commonly used TCP/IP network
protocols require less IT expertise. Therefore,
no special training is required for network
administrators.

5. Benefits
• Excellent performance – it is a very good alternative to
the more expensive Fibre Channel technology.
• No distance limitation – using IP networking solves the
problem with data replication to remote sites.
• Interoperability and flexibility – iSCSI uses standard
Ethernet switches so there is no need to install special
cabling and switches required with Fibre Channel, it can
also run at different Ethernet speed.

6. Benefits
• Compatibility – It is compatible with many
commonly used standards, respected and
recognized by the Internet Engineering Task Force
(IETF).
• Multipathing – iSCSI supports Multipathing to
improve network resiliency.
• Security – iSCSI offers security features such as
Challenge Handshake Authentication Protocol (2-
way CHAP) and Internet Protocol Security (IPsec).

7. iSCSI SANs are especially recommended
to organizations:
• with limited budget and IT infrastructure,
• spread across several physical locations and
willing to consolidate their storage resources,
• requiring remote data replication and disaster
recovery,
• needing immediate and fast access to data
and backup sets,

8. iSCSI SANs are especially recommended
to organizations:
• working as Application Service Providers
(ASPs), Internet Service Providers (ISPs) or
Storage Service Providers (SSPs),
• utilizing demanding server Virtualization
projects requiring network storage solutions.

9. Key iSCSI Terms
• IQN: iSCSI Qualified Names are used to identify both
targets and initiators.
• Target: Storage resource on an iSCSI server.
• Initiator: A Client is called an initiator.
• Node: A single iSCSI target or initiator.
• Portal: A portal is an IP address on a target or initiator.

10. Steps: Creating an iSCSI volume
Step 1: Create LVM Drive for LUNs (Logical Unit
Number)
Step 2: Create Logical Volumes for LUNs
Step 3: Define LUNs in Target Server

11. Commands to Create LVM Drive
Check the drive first:
# fdisk -l /dev/vda
Now, Create partition on that drive:
# fdisk -cu /dev/vda
• The option ‘-c‘ switch off the DOS compatible
mode.
• The option ‘-u‘ is used to listing partition tables,
give sizes in sectors instead of cylinders.

12. Commands to Create LVM Drive
# fdisk -cu /dev/vda
Choose n to create a New Partition:
Command (m for help): n
Choose p to create a Primary partition:
Command action
e extended
p primary partition (1-4): p

13. Commands to Create LVM Drive
Give a Partition number which you need to
create:
Partition number (1-4): 1
Define the size of that partition, use the default
settings to use full size of Drive.
Choose the type of partition:
Command (m for help): t

14. Commands to Create LVM Drive
Choose which partition want to change the type:
Selected partition 1
Hex code (type L to list codes): 8e
Changed system type of partition 1 to 8e (Linux LVM)
Check the changes by print (p) option to list the
partition table
Command (m for help): p
Write the changes using w to exit from fdisk

15. Commands to Create LVM Drive
• Reboot the system and list the Partition table
using the following fdisk command.
# fdisk -l /dev/vda

16. Commands to Create Logical Volumes
• Create Physical volume:
# pvcreate /dev/vda1
• Create a Volume group with name of iSCSI to
identify the group:
# vgcreate testvg /dev/vda1
• List volume group using vgs or vgdisplay:
#vgs testvg

17. Commands to Create Logical Volumes
• Create one or more Logical volumes:
# lvcreate -L 8G -n lv1 testvg
# lvcreate -L 8G -n lv2 testvg
• List the Physical volume, Volume group, logical
volumes to confirm:
# pvs && vgs && lvs
# lvs

18. Commands to Define LUNs in Target Server
• Install the package scsi-target-utils:
# yum –y install scsi-target-utils
• Start the service
# service tgtd start; chkconfig tgtd on
• Open and edit Target configuration file
‘/etc/tgt/targets.conf’

19. Commands to Define LUNs in Target Server
• Append the following volume definition in target
conf file.
iSCSI qualified name
2 LVs Shared for particular LUN.
Example:
<target iqn.2014-07.com.test:tgt1>
backing-store /dev/testvg/lv1
</target>
• Save and close the file

20. Commands to Define LUNs in Target Server
• Reload the configuration by starting tgd service
# /etc/init.d/tgtd reload
• Verify the available LUNs
# tgtadm --mode target --op show

21. Configure an iSCSI Initiator
• Install the package iscsi-initiator-utils:
# yum –y install scsi-initiator-utils
• Change the initiator name in the following file:
‘/etc/iscsi/initiatorname.iscsi’
• Start the service
# service iscsi start; chkconfig iscsi on

22. Discover the target
Use the iscsiadm command to start the iSCSI
discovery:
# iscsiadm -m discovery -t st -p 192.168.0.10
To show the Information about target:
# iscsiadm -m node

23. Log in to the target
Use the iscsiadm command to log in to
discovered iSCSI target:
# iscsiadm -m node –T <IQN name> -p 192.168.0.10 -l
• To stop using target:
# iscsiadm -m node –T <IQN name> -p 192.168.0.10 –u
To delete all information about a target:
# iscsiadm -m node –T <IQN name> -p 192.168.0.10 –op delete

24. List the iSCSI drives
• By Path
# ls –la /dev/disk/by-path
• By id
# ls –la /dev/disk/by-path