[PVE-User] Unresponsive VM(s) during VZdump

[Mike O'Connor]

Hi Alex

Not in my experience, without this option on spinning rust we get 
problems for single host systems.

I've never seen a snapshot created during backups for KVM on ZFS or 
Ceph, Qemu/KVM is doing the backup processing.

I had a hand built system which used snapshots for Ceph before we moved 
to PBS backup. PBS backup is great, but it caused major issues with 
drives going read only until fleecing was an option.

Mike

On 9/5/2024 8:54 pm, Alexander Burke wrote:
> Hello all,
>
> My understanding is that if the backing store is ZFS, a snapshot of the zvol underlying the guest's disk(s) is instant and atomic, and the snapshot is what gets backed up so fleecing is moot. Am I wrong on this?
>
> I know nothing about Ceph other than the fact that it supports snapshots; assuming the above understanding is correct, does snapshot-based backup not work much the same way on Ceph?
>
> Cheers,
> Alex
> ----------------------------------------
>
> 2024-05-09T10:11:20Z Mike O'Connor<mike at oeg.com.au>:
>
>> I played with all the drive interface settings, the end result was I lost customers because of backups causing windows drive failures.
>> Since fleecing was an option, I've not had a lockup.
>>
>>
>>
>> On 9/5/2024 7:32 pm, Iztok Gregori wrote:
>>> Hi Mike!
>>>
>>> On 09/05/24 11:30, Mike O'Connor wrote:
>>>> You need to enable fleecing in the advanced backup settings. A slow backup storage system will cause this issue, configuring fleecing will fix this by storing changes in a local sparse image.
>>> I see that fleecing is available from PVE 8.2, I will enable it next week once all the nodes will be upgraded to the latest version.
>>>
>>> Thanks for the suggestion.
>>>
>>> In the meantime I found this thread on the forum:
>>>
>>> https://forum.proxmox.com/threads/high-io-wait-during-backups-after-upgrading-to-proxmox-7.113790/
>>>
>>> which mention the max_workers parameter. I change it to 4 for the next scheduled backup and see if there are some improvements (I migrated the affected VMs to catch the new configuration).
>>>
>>> I will keep you posted!
>>>
>>> Iztok
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