Re: [Xen-API] Can't Start any VM's from NFS Repository

[Mike McClurg <mike.mcclurg@xxxxxxxxxx>]

On 09/11/12 09:18, Camron Lent wrote:
> I am not sure where else to turn. This is essentially what happened.
> 
> We had an XCP 1.5 pool with 2 machines as hosts. The storage pool which
> is NFS mounted lost its ability to export the filesystem with the VM
> images on it...
> 
> We contacted the vendor and were able to restore it. However, they had
> recommended that we delete the XCP Pool, recreate it, add the hosts back
> in, and then mount the storage.

As you've noticed, this was bad advice...

> This is where we are now. We can see the storage and the VM images.
> However in XCP Xen Center when looking at the images it's clear that the
> metadata is lost. So we can not see which image or snap-shot belongs to
> which VM. The names are all blank when we look at the storage.

It seems at this point you've already reattached the SR. If you do an SR
scan, it should pick up all the old VDIs that were on the SR.

Like you said, you won't know which VDI belongs to which VM. You could
create a VBD for each of them in dom0, and then mount them in dom0 to
see what's on the disks.

> I've gone down the route of randomly selecting VM's with the hope that
> I'd find the right one... because everything I've tried so far has
> failed. I am able to run the vdh-util to see the top-level VDH's and
> I've tried booting from each level to see if I can get any result. The
> same thing occurs each time. I get "The SR failed to complete the
> operation".

I assume that when you say "randomly selecting VMs," you mean selecting
VDIs, right? Because you had already wiped all of your VMs, and you've
just recovered the VDIs.

You'll have to figure out which VDIs belong to which of your old VMs
(see above). Step two will be to recreate the VMs. You'll have to create
a new VM using a template, and then destroy the blank VDIs that were
created along with it. Then create new VBDs for each of the VDIs that
you've determined belong to that VM. You should be able to start the VM
up, as long as you've got the VBD device numbers in the right order.

> I would be happy if I could just get to the data, but the snapshotting
> process leaves a trail of incremental difference files (at least it
> appears that way). I am currently at a loss as to what to do.

Your VM snapshots were kept in Xapi's database, which you lost. You'll
probably have a bunch of VDIs that will look like they belong to the
same VM. Maybe you'll be able to figure out the latest one based on
filesystem timestamps when you mount them in dom0?

> If anyone knows a trick to try, or how to undo the horrible mistake
> we've made please let me know at camronlent@xxxxxxxxx
> <mailto:camronlent@xxxxxxxxx>
> 

Good luck with this. I'll see if I can get someone from the storage team
to offer more advice.

Mike


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