Stabilizing iSCSI based Virtual Desktops

wponder — Wed, 23 May 2007 15:45:00 GMT

Starting with ESX 3.0.1 iSCSI support was introduced. This opens up the opportunity to leveraging lower cost storage options when hosting virtual desktop instances. The topic of, what disk to store desktop images on, is one that gets tossed around like a hot potato. For some customers it seems like a non-issue. Their cost per gig is the same regardless if its enterprise fibre channel storage or low end storage. Some are not interested in introducing a second architecture into their data center as is the case when considering iSCSI.

For others, cost is an issue, and the possibility of leveraging iSCSI is very important to them. In my lab, I currently have an older NAS array
with around ½ terabyte of usable storage.

Several months back I decided it was time to start running some virtual desktops on it and see what performance is like.
I quickly realized, there was a little bug where ESX would not see iSCSI LUNs on my NAS appliance. So, for some time I ran an unsupported patch. Because it was unsupported, I left things as is and did not really watch the performance. This past week I was building some Solaris Express VMs for another test, when all hell broke
loose. Somehow, during the eternal boot of the Solaris VM my ESX system hosed. Because I was having such an issue, I decide it was time to do
some basic patch management. In all fairness, I was way behind on all my ESX patches. I had actually moved more VMs to iSCSI than I had
realized. All of which where very important.

The moral of the story is now, an official iSCSI patch is available for ESX 3.0.1. Patch number ESX-6657345 solves previous issues with iSCSI. After loading the patch on my systems I still was having an issue though. My ESX hosts could not log into the iSCSI target. What was really odd, is my NAS box did not see
the login attempts. It logs denied connection attempts and it saw nothing. The messages log on my ESX hosts were logging connection
refused. I tried removing and adding the iSCSI adapter through the VIC which also did not work. Finally, I got everything working and very
stable using the following steps.

Download patch ESX-6657345 and install it using esxupdate

From the VIC under configuration, storage adapters disable any iSCSI adapters
From the ESX console run esxcfg-swiscsi –d
From the ESX console run esxcfg-swiscsi –k
From the ESX console delete any iSCSI targets listed in /var/lib/iscsi/bindings
From the ESX console run esxcfg-swiscsi –e
From the ESX console run esxcfg-swiscsi –s
From the VIC under configuration, storage adapters enable any iSCSI adapters
From the VIC under configuration storage adapters rescan for the targets

After completing this, I was back in business and it has been much more stable. Soon I hope to share how some virtual desktops are working via
iSCSI, stay tuned.

Virtual Desktop Blog

Stabilizing iSCSI based Virtual Desktops