ZFS and snapshot backups?

[gkovacs]

I am currently testing Proxmox 3.4 installed on ZFS for deployment in our mixed OpenVZ/KVM environment. It has become apparent that VZDump does not support snapshot backups on ZFS (only suspend), which is not acceptable for our uses.

INFO: starting new backup job: vzdump 100 --remove 0 --mode snapshot --compress lzo --storage backup --node pve
INFO: Starting Backup of VM 100 (openvz)
INFO: CTID 100 exist mounted running
INFO: status = running
INFO: mode failure - unable to detect lvm volume group
INFO: trying 'suspend' mode instead
INFO: backup mode: suspend

I have a couple of questions about ZFS and backups:

1. is VZDump expected to support ZFS snapshots for backup anytime soon? (is anyone working on it / is it possible at all?)

2. are KVM backups suspend only as well when on local ZFS? (I can't test yet, as I'm running under Virtualbox)

3. is it possible to add LVM storage on top of ZFS somehow, thereby enabling snapshot backup capability?

 

[redmop]

As to number 3, make a zvol in zfs, use pvcreate and vgcreate, then add the volume group to proxmox.

As for number 2, you can disable the kvm extensions in proxmox to allow qemu to run vms under proxmox.

 

[gkovacs]

Can someone please confirm if KVM backups support snapshots when PVE is installed on ZFS?

 

[wolfgang]

Hi,
it is not implemented yet but will come soon.

 

[gkovacs]

Hi,
it is not implemented yet but will come soon.

Hi wolfgang,

please clarify, what is coming soon:
- ZFS snapshot backups for KVM and OpenVZ?
- or for KVM only?

What about adding LVM storage on top of ZFS at install? Any chance of that happening?

 

[wolfgang]

ZFS snapshot backups for KVM only will come.

adding a LVM storage on top of zfs will so long you reboot the machine.
zfs will maybe change the device name on reboot.

 

[gkovacs]

ZFS snapshot backups for KVM only will come.

That's good news, although OpenVZ will be even better.
So how does it work now, does the KVM VM gets stopped/suspended for the entire duration of the backup?

adding a LVM storage on top of zfs will so long you reboot the machine.
zfs will maybe change the device name on reboot.

Is this related to the bug where the PVE installer creates the zpool from /dev/sdX devices, and not /dev/by-id/ names?
https://bugzilla.proxmox.com/show_bug.cgi?id=626

 

[wolfgang]

No, this is another problem.
The problem is that LVM follow the link from /dev/zvol/* and end at /dev/zdx and there ZFS could change the numbers on reboot.

 

[Shazan]

So how does it work now, does the KVM VM gets stopped/suspended for the entire duration of the backup?

No, it doesn't get stopped or suspended. It is a live backup.

 

[gkovacs]

No, this is another problem.
The problem is that LVM follow the link from /dev/zvol/* and end at /dev/zdx and there ZFS could change the numbers on reboot.

Ok, couple of questions:
- Is it a bug of ZFS or LVM?
- Can this problem be solved somehow manually by a user or by Proxmox developers?

The reason I'm asking is because adding LVM on top of zvol would solve a lot of problems for users running OpenVZ (snapshot backups, quota).

 

[wolfgang]

This was a Zfs related bug it should be fix it in 0.6.4 So you can upgrade or repros are on 0.6.4.1

 

[gkovacs]

This was a Zfs related bug it should be fix it in 0.6.4 So you can upgrade or repros are on 0.6.4.1

That is great news!

Do you think you could modify the Proxmox installer so it could create LVM+ext4 on top of ZFS zvols? This would solve a lot of problems for us going forward... we could use the awesome RAIDZ and ZIL/L2ARC features, but also the snapshotting of LVM and the quota on ext4 which are all very important for OpenVZ.

 

[Sasha Splinter]

I bag a pardon for possible misunderstanding. But here https://pve.proxmox.com/wiki/Storage:_ZFS as i can understand exactly snapshots on ZFS are promised. Is it future plans, or abandoned ones?
How we should understand that wiki part? As abstract ZFS description, that doesn't concern ProxMox itself?

PS Yes, i already have Commercial Support Subscription )))