Friday, 10 August 2012

Setting up iSCSI (target/server and initiator/client) on RHEL6.0

It's quite easy to setup an iSCSI environment on Red Hat Enterprise Linux. Try this easy setup to get a better understanding of iSCSI.
1.    Two (virtual) machines, a server and a client
2.    Access to the "RHEL Cluster-Storage" channel on Red Hat Network.
N.B. SELinux must be disabled when using this recipe, iptables tcp port 3260 must be opened on the server.
On the server execute these commands to setup a 100 Mb iSCSI target. This target can later be mounted on the client(s).
# yum install scsi-target-utils
# cat /etc/tgt/targets.conf
backing-store /iscsi1.img
# dd if=/dev/zero of=/iscsi1.img bs=1024 count=102400
# chkconfig tgtd on
# service tgtd start
Now on (all) client(s) follow these steps. (Please pay attention that only one client was give access in the configuration example above;
# yum install iscsi-initiator-utils
Start iscsi daemon.
# service iscsi start
To see what IQNs are available, run:
# iscsiadm -m discovery -t sendtargets -p

The result is a list of IQN(s) available. This discovery is a mandatory step of connecting to the iSCSI target.
Login to the iSCSI target:
# iscsiadm -m node -T -p -l
If that all works, you have new SCSI devices available, check dmesg and start iscsi at boot time:
# chkconfig iscsi on
In this example the iSCSI target does not have a filesystem. Create it on the client and mount it at boot time:
# fdisk /dev/sda
# mkfs.ext3 /dev/sda1
# echo "/dev/sda1 /mnt ext3 defaults,_netdev 0 0" >> /etc/fstab
You are done, but these commands are quite useful when connecting to an unknown iSCSI device.
To see more about the IQN:
# iscsiadm -m node -T -p

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