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

[Denis Cardon <denis.cardon@xxxxxxxxxxxxxxxxxxxxxx>]

Hi Juan,

> Thanks.  We actually still have the original VMs.  Believe it or not,
> when we destroyed the Pool, the VM information went with the master.  So
> when we recreated, they transferred over.
>
> So I still have the VM and their UIDs as they were in the previous pool.
It looks like if it was a SR forget. I once did a sr-forget on a stale 
lvmoiscsi connexion (very bad idea) and had to remap all the vdi to the 
right VM afterward (took me some time). However I have not much 
knownledge about nfs SR.
> For whatever reason, I just can not see what we think was the running
> .vhd file when we go to the storage repository in Xen Center.  I have
> some 200+ files there but only about 100 of them show up when I look
> through the XenCenter software.
VHD file can have a property "hidden" set to true or false. You can 
check the command /usr/bin/vhd-util query -vfspd  -n 
/var/run/sr-mount/xxxxxxx-xxxxx-xxxxxx-xxxxx/xxxxxxxxxxxxxx.vhd
The VHD that you don't see in xencenter are probably the hidden ones. I 
think those are the "base copy" vdi that you get when doing a snapshot 
(http://support.citrix.com/article/CTX122978).
If the vdi are seen by xencenter, I think you can also use "xe vdi-list 
read-only=false" to get vdi that should be mountable. Afterward, you 
have to attach the vdi to a running vm and look at it to known to which 
VM it belongs.
hope this help,

Denis


> I will post to xen-devel@xxxxxxxxxxxxxx  That was a good idea.
>
> Juan
>
>
>
> -----Original Message-----
> From: xen-api-bounces@xxxxxxxxxxxxx
> [mailto:xen-api-bounces@xxxxxxxxxxxxx] On Behalf Of Mike McClurg
> Sent: Friday, November 09, 2012 4:03 AM
> To: Camron Lent
> Cc: xen-api@xxxxxxxxxxxxx
> Subject: Re: [Xen-API] Can't Start any VM's from NFS Repository
>
> 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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--
Denis Cardon
Tranquil IT Systems
Les Espaces Jules Verne, bâtiment A
12 avenue Jules Verne
44230 Saint Sébastien sur Loire
tel : +33 (0) 2.40.97.57.55
http://www.tranquil-it-systems.fr


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