Re: [ovirt-users] Using Microsoft NFS server as storage domain
On Thu, Jan 21, 2016 at 2:54 PM, Pavel Gashev <Pax(a)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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