The Importance of HCLs

This is going to get a complete and total “DUH” from many of my system administrator friends out there, but I thought I would just share my experience as well … and why I should never just expect that a little extra work will be worth it in the end.

We run XenServer here on campus for our virtualization infrastructure and have been relatively pleased with how it has fit out needs. While updates should be trivial, a decision I made definitely complicated things far beyond what they needed to be.

For all other servers on campus we use Adaptec RAID controllers and have been very happy with them. We also used them in our storage boxes (running Ubuntu 12.04). They have been rock-solid and so I wanted to stick with what we know when it came to the XenServer host boxes as well.

The only problem is that Adaptec is not well-supported by XenServer. You can do it (and we did originally) by creating driver disks every time a new kernel is installed. That means that normal updates can cause headaches as you wait for the DDK to drop, then create the driver disk, and then hope that the driver installation works when you install the update. We did it a number of times and it worked fine, but it was not ideal.

It also caused an issue where we could not move from XenServer 6.1 to the new, open source, XenServer 6.2 at least in part because we were using Adaptec RAID controllers. That was enough. So I finally sat down with the HCLs for XenServer 6.0.2, XenServer 6.1, and XenServer 6.2 and worked to find a RAID card to help us with the upgrade to XenServer 6.2 and also push us into the future as well.

Needless to say, I found one, and I wish I would have done this sooner.

Working with a supported RAID controller has the following benefit, so far:

  • installation is faster because I do not need to install separate drivers for the RAID controllers
  • updates as faster because I do not need to have driver disks for each kernel update
  • upgrades are faster (and possible) because I can now do an upgrade to the XenServer pool without needing to do a fresh reinstall and migration of VMs
  • I have peace of mind because if something happens, I’m just a reinstall away from a working box again … regardless of whether I have the driver disks anymore or not

So I’ve learned my lesson. I am now going to pour over the HCL for a given software package before I go off making decisions. Fortunately we have use for the Adaptec cards I am replacing … and I am very happy to finally be rid of them soon in our XenServer host boxes.

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