Thursday, July 05, 2007

Linux ISCSI with EMC2 AX150 SAN

Finally got my new external SAN file system up and running and attached to the linux server farm using ISCSI (i.e. SCSI over a standard network interface--all devices are attached to the same network switch, but otherwise no special equipment needed).

The Problems
1. EMC^2 needs to be told they are missing an equal sign.
2. Their documentation is terrible.
3. Their SAN management software doesn't yet work on RHEL5, but my version of RHEL4 did not support the linux ISCSI initiator software.

First, review the ISCSI terminology a bit. See the links from my previous post for nice reviews. In short, your SAN device is your ISCSI target. You will mount it as a SCSI device over a network connection to a linux server (or Windows 2003 if you prefer), where it can be treated like an ordinary file system. The linux host runs the ISCSI initiator and acts as a client, if you are more comfortable with client-server terminology.

The basic steps (besides powering up the SAN) are as follows:
1. Install iscsi initiator software (use up2date or yum--"yum iscsi-initiator") on your linux server. You probably want to update your kernel as well. This was my first problem, since up2date on RHEL4 refused to update my kernel (linux 2.6.9-5), and attempting to start the ISCSI daemon on linux failed because of missing kernel modules. So I upgraded to RHEL5. This whole set of sub-steps was wildly unclear in the EMC2 documentation.

2. Set up your SAN's network configuration from your linux server. EMC2's tools (Navisphere, Powerpath) worked fine on RHEL4 but not RHEL5, so I wound up doing this step from a second linux server that still ran RHEL4. I just used IP addresses from our pool.

3. Configure your SAN's disk pool, RAID, etc. EMC2 provides a nice web tool, Navisphere Express, to do this.

4. Fire up the ISCSI client on your linux server. See the README at for everything you need, although it took a while for me to digest it. At the end, run "fdisk -l" and you should see your new /dev/sdX devices. If you don't, but all the iscsiadm commands are working fine, it could mean that you completed step #2 but not #3.

5. Partition and format your devices in the usual way with fdisk, etc. See for example Mount the file systems and you should be in business.

1 comment:

Whitemice Consulting said...

Are you using CHAP authentication with your SAN? We have an AX4-5 and are struggling to connect out CentOS5 boxes to the SAN, authentication seems to not work.