[PVE-User] PBS backup/restore issue

[Thomas Lamprecht]

Hi!

On 24.02.21 12:53, Eneko Lacunza wrote:
> El 24/2/21 a las 11:34, Stefan Reiter escribió:
>> On 2/23/21 8:46 AM, Eneko Lacunza wrote:
>>> Yesterday I hit a problem with PBS. My sequence of actions was:
>>>
>>> 1.a Install debian 10 VM (updated to latest, only system utilities and SSH server)
>>> 1.b Add SSH access key to root
>>> 1.c Shutdown VM
>>> 1.d Backup to PBS and to NFS vía regular backup.
>>> 1.e Start VM and install various packages - all OK.
>>> 1.f Stop VM
>>>
>>> 2.a Restore VM from PBS backup
>>> 2.b Start VM and install various packages - apt complains about no newline in linux-image-amd64 file manifest, can't install new packages.
>>> 2.c Stop VM
>>>
>>> 3.a Restore VM from NFS regular backup
>>> 3.b Start VM and install various packages - all OK.
>>>
[snip]

> My original restores were to a ceph storage (r2 on HDD with SSD journal/DB). So i have restored again both, to that ceph storage:
[snip]

> 
> Hope this info helps you to replicate the issue.

FYI: Stefan could replicate it and send a patch[0] which is included now.

It boiled down to caches not being flushed to disk for storage attached through
user-space libraries (vs. kernel) by QEMU in the PBS restore case.

In your case you probably do not have the "KRBD" checkbox ticked for the Ceph
storage entry in PVE, so the user-space librbd is used for accessing that storage
through QEMU, where this issue then hit on restore.

If you want to try the fix out, there's a new QEMU package available on pvetest:

http://download.proxmox.com/debian/pve/dists/buster/pvetest/binary-amd64/pve-qemu-kvm_5.2.0-2_amd64.deb
sha256sum: 6a086e0b669447f0b8a7899f9194a26785e6b0070f3dec1be4f95067bc707c7a

cheers,
Thomas

[0]: https://lists.proxmox.com/pipermail/pve-devel/2021-February/047131.html