On Thu, Jan 21, 2016 at 2:54 PM, Pavel Gashev <Pax@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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