iSCSI

Internet Small Computer System Interface

iSCSI

• iSCSI is a TCP/IP based protocol for sendingSCSI commands over IP based networks.

• This allows iSCSI infrastructure to extendbeyond a local LAN, and be used on a WAN oreven over the internet.

iSCSI

Benefits

• Low cost – iSCSI uses the existing networkinfrastructure so there is no need to buyexpensive equipment.

• Easy installation and maintenance of iSCSISANs – commonly used TCP/IP networkprotocols require less IT expertise. Therefore,no special training is required for networkadministrators.

Benefits

• Excellent performance – it is a very good alternative tothe more expensive Fibre Channel technology.

• No distance limitation – using IP networking solves theproblem with data replication to remote sites.

• Interoperability and flexibility – iSCSI uses standardEthernet switches so there is no need to install specialcabling and switches required with Fibre Channel, it canalso run at different Ethernet speed.

Benefits

• Compatibility – It is compatible with manycommonly used standards, respected andrecognized by the Internet Engineering Task Force(IETF).

• Multipathing – iSCSI supports Multipathing toimprove network resiliency.

• Security – iSCSI offers security features such asChallenge Handshake Authentication Protocol (2-way CHAP) and Internet Protocol Security (IPsec).

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,

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.

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.

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

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.

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

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

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 tableCommand (m for help): p

Write the changes using w to exit from fdisk

Commands to Create LVM Drive

• Reboot the system and list the Partition table using the following fdisk command.

# fdisk -l /dev/vda

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

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

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’

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

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

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

Discover the target

Use the iscsiadm command to start the iSCSIdiscovery:# iscsiadm -m discovery -t st -p 192.168.0.10

To show the Information about target:# iscsiadm -m node

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

List the iSCSI drives

• By Path

# ls –la /dev/disk/by-path

• By id

# ls –la /dev/disk/by-path