On Mon, Jul 22, 2019 at 8:07 PM Strahil <hunter86_bg@yahoo.com> wrote:

I have a theory... But after all without any proof it will remain theory.

The storage volumes are just VGs over a shared storage.The SPM host is supposed to be the only one that is working with the LVM metadata, but I have observed that when someone is executing a simple LVM command (for example -lvs, vgs or pvs ) while another one is going on on another host - your metadata can corrupt, due to lack of clvmd.

As a protection, I could offer you to try the following solution:
1. Create new iSCSI lun
2. Share it to all nodes and create the storage domain. Set it to maintenance.
3. Start dlm & clvmd services on all hosts
4. Convert the VG of your shared storage domain to have a 'cluster'-ed flag:
vgchange -c y mynewVG
5. Check the lvs of that VG.
6. Activate the storage domain.

Of course test it on a test cluster before inplementing it on Prod.
This is one of the approaches used in Linux HA clusters in order to avoid LVM metadata corruption.

Best Regards,
Strahil Nikolov

On Jul 22, 2019 15:46, Martijn Grendelman <Martijn.Grendelman@isaac.nl> wrote:

Hi,

Op 22-7-2019 om 14:30 schreef Strahil:

If you can give directions (some kind of history) , the dev might try to reproduce this type of issue.

If it is reproduceable - a fix can be provided.

Based on my experience, if something as used as Linux LVM gets broken, the case is way hard to reproduce.

Yes, I'd think so too, especially since this activity (online moving of disk images) is done all the time, mostly without problems. In this case, there was a lot of activity on all storage domains, because I'm moving all my storage (> 10TB in 185 disk images) to a new storage platform. During the online move of one the images, the metadata checksum became corrupted and the storage domain went offline.

Of course, I could dig up the engine logs and vdsm logs of when it happened, but that would be some work and I'm not very confident that the actual cause would be in there.

If any oVirt devs are interested in the logs, I'll provide them, but otherwise I think I'll just see it as an incident and move on.

Best regards,
Martijn.

On Jul 22, 2019 10:17, Martijn Grendelman <Martijn.Grendelman@isaac.nl> wrote:

Hi,

Thanks for the tips! I didn't know about 'pvmove', thanks.

In the mean time, I managed to get it fixed by restoring the VG metadata on the iSCSI server, so on the underlying Zvol directly, rather than via the iSCSI session on the oVirt host. That allowed me to perform the restore without bringing all VMs down, which was important to me, because if I had to shut down VMs, I was sure I wouldn't be able to restart them before the storage domain was back online.

Of course this is a more a Linux problem than an oVirt problem, but oVirt did cause it ;-)

Thanks,
Martijn.

Op 19-7-2019 om 19:06 schreef Strahil Nikolov:

Hi Martin,

First check what went wrong with the VG -as it could be something simple.

vgcfgbackup -f VGname will create a file which you can use to compare current metadata with a previous version.

If you have Linux boxes - you can add disks from another storage and then pvmove the data inside the VM. Of course , you will need to reinstall grub on the new OS disk , or you won't be able to boot afterwards.

If possible, try with a test VM before proceeding with important ones.

Backing up the VMs is very important , because working on LVM metada

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