On Thu, Jan 21, 2016 at 2:54 PM, Pavel Gashev <p...@acronis.com> wrote:
> Hello,
>
> First of all I would like to ask if anybody has an experience with using
> Microsoft NFS server as a storage domain.
>
> The main issue with MS NFS is NTFS :) NTFS doesn't support sparse files.
> Technically it's possible by enabling NTFS compression but  it has bad
> performance on huge files which is our case. Also there is no option in
> oVirt web interface to use COW format on NFS storage domains.

You can
1. create a small disk (1G)
2. create a snapshot
3. extend the disk go the final size

And you have nfs with cow format. The performance difference with one snapshot
should be small.

> Since it looks like oVirt doesn't support MS NFS, I decided to migrate all
> my VMs out of MS NFS to another storage. And I hit a bug. Live storage
> migration silently corrupts data if you migrate a disk from MS NFS storage
> domain. So if you shutdown just migrated VM and check filesystem you find
> that it has a lot of unrecoverable errors.
>
> There are the following symptoms:
> 1. It corrupts data if you migrate a disk from MS NFS to Linux NFS
> 2. It corrupts data if you migrate a disk from MS NFS to iSCSI
> 3. There is no corruption if you migrate from Linux NFS to iSCSI and vice
> versa.
> 4. There is no corruption if you migrate from anywhere to MS NFS.
> 5. Data corruption happens after 'Auto-generated for Live Storage Migration'
> snapshot. So if you rollback the snapshot, you could see absolutely clean
> filesystem.

Can you try to create a live-snapshot on MS NFS? It seems that this is the
issue, not live storage migration.

Do you have qemu-guest-agent on the vm? Without qemu-guest-agent, file
systems on the guest will no be freezed during the snapshot, which may cause
inconsistent snapshot.

Can you reproduce this with virt-manager, or by creating a vm and taking
a snapshot using virsh?

> 6. It doesn't depend on SPM. So it corrupts data if SPM is on the same host,
> or another.
> 7. There are no error messages in vdsm/qemu/system logs.
>
> Yes, of course I could migrate from MS NFS with downtime – it's not an
> issue. The issue is that oVirt does silently corrupt data under some
> circumstances.
>
> Could you please help me to understand the reason of data corruption?

Please file a bug and attach:

- /var/log/vdsm/vdsm.log
- /var/log/messages
- /var/log/sanlock.log
- output of  nfsstat during the test, maybe run it every minute?

> vdsm-4.17.13-1.el7.noarch
> qemu-img-ev-2.3.0-31.el7_2.4.1.x86_64
> libvirt-daemon-1.2.17-13.el7_2.2.x86_64
> ovirt-engine-backend-3.6.1.3-1.el7.centos.noarch
>
> Thank you
>
>
>
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