zstd: error 25 : Write error : No space left on device (cannot write compressed block)

[fabian]

with rclone vfs-cache off, vzdump makes a local cache copy of the hole container -> no space left. Backup failed and container starts again.

this is only true for suspend backups, and there it is true irrespective of backup storage type or settings:

• stop mode: container is simply mounted, tar archive is created directly from mounted volumes directly onto backup storage. only temporary duplicate storage usage is firewall and container guest config in $tmpdir
• suspend mode: container volumes are rsynced to temprorary directory, container is suspended, volumes are rsynced incrementally on top of first synced copy, container is resumed, tar archive is created from temporary copy onto backup storage. temporary space usage is roughly equal to total space usage of backed-up volumes
• snapshot mode: container volumes are snapshotted, snapshots are mounted, tar archive is created directly from mounted snapshots onto backup storage. temporary space usage: firewall and container config + whatever the snapshot itself consumes on the source storage (usually the amount of data written by the guest during the backup + some metadata overhead, but depends on storage)

so if you do a stop mode backup and see massive space usage outside of the backup storage caused by the backup something is wrong with your setup (most likely - your backup storage is not mounted correctly!)

 

[proofy2]

Sorry if it seems like I'm trying to be annoying. I just want to help.
Personally, I have now found a solution. I deleted all other containers and unnecessary files and thus had enough local space free to create another backup. Then I could use this backup to move to another server.

I was able to show that there are conditions where vzdump creates large files locally in stop mode. In my opinion, this cannot be due to the backup configuration of vzdump/proxmox. Whether rclone together with pcloud is optimally configured for proxmox should not matter. vzdump should issue appropriate warnings.

Unfortunately, I don't know any way to simulate this behaviour and so cannot demonstrate it for everyone. I am still available for questions, but I will otherwise stop my proof activities that this might be a bug.
Misunderstandings due to the language barrier can also still be a problem, which is why I have had help.


Translated with www.DeepL.com/Translator (free version)

 

[fabian]

you are not annoying I still think something is not working correctly with you "automount" setup and your backup ends up on the / partition or that rclone caches stuff both with and without the 'vfs cache' option - there is no other reasonable explanation for the error messages and behaviour. the only time vzdump does a temporary copy is with suspend mode backups - and there the logs clearly indicate this (by logging first and second rsync phase for the temp copy separately, before creating the archive).