Linux BLog: How To Setup ISCSI On Linux(RedHat)

How To Setup ISCSI On Linux(RedHat)

Definitions:

iSCSI initiator : the endpoint that initiates a iSCSI session. An iSCSI initiator sends SCSI commands over an IP network. It’s the client endpoint.

iSCSI Target : refers to a storage resource located on an iSCSI server (most of the time it’s a “storage array”). It’s the server endpoint.

LUNs (Logical Number Units): number used to identify a logical unit, which is a device addressed by the SCSI protocol (thus Fiber Channel or iSCSI). It usually represents slices of large RAID disk arrays.

IQN (iSCSI Qualified Name) : iSCSI name of the target or initiator.

On the Storage Server:

Enable and configure the iSCSI Target on your storage server.

Mine is a QNAP Turbo NAS. I’ve got 1 target with 5 LUNs configured.

SCSI Portal

X Enable iSCSI Target Service

iSCSI Service Port: 3260

mytarget (iqn.2004-04.com.qnap:ts-859:iscsi.mytarget.c5884b) Connected

id:0 - lun1 ( 2024.00 GB) Enabled

id:1 - lun2 ( 2024.00 GB) Enabled

id:2 - lun3 ( 2024.00 GB) Enabled

id:3 - lun4 ( 2024.00 GB) Enabled

id:4 - lun5 ( 1804.13 GB) Enabled

I have two network interfaces:

1) for QNAP management, IP : 10.0.0.5

2)iSCSI access, directly connected to the server : 192.168.0.1

For more security you can enable “LUN masking”. It will restrain iSCSI target to be accessed to only by the initiator of your client (the client initiator name IQN can be found on /etc/iscsi/initiatorname.iscsi).

On the Linux client (see tips ** for VMware configuration) :

Install “iscsi-initiator-utils” on the server that will connect to the iSCSI volume:

# rpm –Uvh iscsi-initiator-utils-6.2.0.865-6.el5.x86_64.rpm

Set up iscsi automatic start on boot and start iscsi services:

# chkconfig iscsid on

# service iscsid start

# chkconfig iscsi on

# service iscsi start

Discover your iSCSI targets:

# iscsiadm -m discovery -t st -p 192.168.0.1

In my case it will show 2 targets (one for each network connection):

# iscsiadm -m node -T iqn.2004-04.com.qnap:ts-859:iscsi.mytarget.c5884b -p 192.168.0.1 -l

Add automatic login at boot :

# iscsiadm -m node -T iqn.2004-04.com.qnap:ts-859:iscsi.mytarget.c5884b -p 192.168.0.1 --op update -n node.startup -v automatic

As I have another access to the target, I will disable it in order to not disturb the previous configuration:

# iscsiadm -m node -T iqn.2004-04.com.qnap:ts-859:iscsi.mytarget.c5884b -p 10.0.0.5 --logout

# iscsiadm -m node -T iqn.2004-04.com.qnap:ts-859:iscsi.mytarget.c5884b -p 10.0.0.5 --op update -n node.startup -v manual

At this point you will see the iSCSI LUNs as block devices on your client.

On my system the five iSCSI block devices are /dev/sdc, sdd, sde, sdf and sdg.

You will have create partitions and format them to either standard Linux partition or LVM partition.

I chose LVM because I need large file systems.

You can use parted or fdisk (if < 2To), see article: ” How To Make Partitions Larger Than 2To With Parted GPT Support“.

So here is the result:

# fdisk -l

Disk /dev/sdc: 2173.2 GB, 2173253451776 bytes