Building an inexpensive SAN with RHEV's iSCSI target software

With the right equipment, RHEV's iSCSI target software can build an inexpensive SAN, which is great for cost-conscious IT shops.

Using Red Hat Enterprise Virtualization's iSCSI target software is an easy way to build an inexpensive SAN, which is great for cost-conscious IT shops that want to deploy advanced features, such as live migration and high availability.

Everything you need to build a storage area network (SAN) with an iSCSI target comes with the Red Hat Enterprise Linux software that runs RHEV-M. Just follow these steps.

Installing and configuring the iSCSI target software

First, make sure to have the proper disk devices installed for use with the SAN. Use the command fdisk -cul to check the names of available disks on your RHEV-M server. (I'll assume the host has a dedicated disk called /dev/sdb.)

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Next, open a root terminal on the RHEV-M machine. Enter the command yum -y install scsi-target-utils, which will install the iSCSI target software on the server. After the installation, use chkconfig tgtd on to ensure that the iSCSI process starts when the server boots.

Now, open the configuration file /etc/tgt/targets.conf and include the following text at the end of the file:

<target iqn.2012-08.com.example.rhev:target>        
           backing-store /dev/sdb
</target>

Next, run the command service tgtd start to initiate the iSCSI target software. You now have your own inexpensive SAN.

Connecting the hosts to the iSCSI SAN

Next, you need to connect your RHEV-H hosts to the inexpensive SAN. First, make the SCSI storage domain available to the cluster in RHEV-M. Log in to the RHEV-M interface. (You can find it at the URL https://your-rhev-host:8443/RHEVManager.) Then, expand the system item in the left pane. Select the Default data center and click New Domain. You'll now see the New Domain dialogue.

New Domain dialogue

Enter the storage properties in the New Domain dialogue.

When installing RHEV, you entered the default storage domain, which should be set to iSCSI, assuming that you planned on using iSCSI for the storage. Therefore, the New Domain dialogue will automatically be set to the Data / iSCSI Storage Type. The only thing you need to do is give a name to the new storage domain and enter the IP address of the RHEV-M hosts where an iSCSI target is located.

You don't need to enter any user authentication information, because the iSCSI nodes already reside within a secure network. After entering the required information, click OK to connect to the iSCSI target storage. At this point, the RHEV-M console will list the iSCSI target. Select it and click the Login button to make the iSCSI available for all hosts in the default data center.

After logging in, open the iSCSI target, and click on the LUN that you want to use as the default data domain. After selecting it, it will be available to all hosts in your cluster.

Connecting the hosts to the iSCSI SAN

Select the LUN you want to use as the default data domain to make it available for all hosts.

Attaching the ISO domain

Apart from a storage domain, you'll also need an ISO domain, which will make ISO images available for the installation of virtual machines. You've already defined the default ISO domain while installing RHEV, and now you need to make the ISO domain available to the data center.

To do this, from the RHEV-M interface, select the data center and click the Storage tab in the lower part of the screen. (There are two storage tabs. Click the tab located on the right.) On this tab, click Attach ISO.

Attaching the ISO domain

Click Attach ISO on the lower part of the screen

At this point, you can select the ISO share and attach it to your default data center. Next, you'll need to copy the ISO files to the directory. Use a tool, such WinSCP, which is great for copying files from FTP servers. Once you've populated the ISO share, you can start installing virtual machines.

This was first published in August 2012

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