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Wednesday, November 19, 2008

Wondering where's your CDROM gone in your HVM domain?

That's what I've been wondering since a couple of weeks ago...

I have a couple of Microsoft Windows Server 2003 Enterprise HVM domains running on Sun xVM shipped with Solaris Express Community Edition (build 101). Yes, I know... but it's not my fault! ;) When I installed the machine I had that "bad feeling" you perceive, because I had to manually trick the virtual machine definition, dumped by a
# virsh dumpxml [hvm-domain]
command as suggested by many documents I found googling. One of them was an official Sun Microsystems technical brief titled Install Sun xVM hypervisor & use it to configure domains found on the excellent BigAdmin portal. Page 8 of this brief states:
There is a bug 6648448 with respect to the Windows 2003 guest and the CD. The install will halt with a Windows error message with regard to access to the CDROM.
By using the suggested workaround I happily resolved the problem. That problem.

Indeed, when I had to configure an Active Directory instance in one of these machines, at the end of the DNS configuration I was asked for Windows Server 2003 CD 2. No problem, thought I, just do a
# virsh block-attach [hvm-domain] file:/your/iso/file hdb:cdrom r
but it was impossible for me to succeed in mounting the cdrom. The following error was raised:
Error: Device [put your number here] (vbd) could not be connected. Backend device not found.

Nevertheless the device seemed to be created because the cdrom was appearing in the block-list output. The system couldn't see anything, nor the empty CDROM, indeed. The worst thing, I didn't want to stop the machine just in the middle of the Active Directory installation.

At the end I desperately gave up and stopped the machine, checked the dumpxml output and restarted the machine. The block-attach call now succeeded. What was happening to my HVM domain? I didn't know and probably still do not, but the changelog for Solaris Express Community Edition build 102 makes me think that I hit the following bug:
Empty CD-ROM disappears from HVM domains
So, where was my cdrom? It had simply disappeared.

If you are experiencing a similar error and you're running Solaris Express Community Edition up to build 101, I suggest you to give up and restart the domain. At least, you'll spare some time banging your head against the wall.

Another bad thing after the initial happiness (I was indeed eager to update my system) was the following post on the Solaris Express announcement forum:
Due to the following bug, I have removed build 102 from the Download page.

6771840 zpool online on ZFS root can panic system

It apparently may cause data corruption and may have been implicated in damage to one or more systems that have upgraded to build 102 or beyond.

We will remove it from the SDLC on Monday. I will notify about the schedule for a repsin.

I'll have to wait some more time to be able to insert a CDROM on an already running HVM domain but I want to put in a word for xVM: except for these... minor glitches ;) I'm very pleased with it and I'm looking forward to trying Sun xVM Server as soon as Sun will ship it.

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