Question About LXC Backups and Temporary Storage Requirements

[jdomlin]

Hi everyone,

If this has already been answered elsewhere, apologies—I couldn’t find it.

I understand that VMs can stream backups directly to PBS storage without needing local space.
However, for LXC containers, it seems they require a local tmpdir during backup.

Is that correct?
If so, this seems problematic.
For example, if you have an LXC with 1TB of disk, you’d need roughly 1TB of free space on every Proxmox node in the cluster just to perform backups.

That doesn’t feel practical.
Nodes shouldn’t need to reserve that much local storage just for backups.
Ideally, all backup-related storage should remain on the storage nodes, centralized for the cluster.

As it stands, we have several LXC containers that aren’t backed up because of this limitation.

Has anyone found a solution or workaround for this?

 

[fabian]

for containers, it depends which backup mode you use.

for snapshot mode, the backup will be taken directly from a storage-level snapshot, no extra copy needed.
for suspend mode, a temporary copy needs to be made (first it will be copied while the container is running, then the container is suspended, then an incremental copy is done, then the container is resumed, then the backup is taken from the copy)
for stop mode, the backup will be taken directly from the volumes, no extra copy needed

note that if you select "snapshot" mode but your config doesn't support it, the backup will be downgraded to "suspend" mode - this will be visible in the backup log!

 

[jdomlin]

for containers, it depends which backup mode you use.

for snapshot mode, the backup will be taken directly from a storage-level snapshot, no extra copy needed.
for suspend mode, a temporary copy needs to be made (first it will be copied while the container is running, then the container is suspended, then an incremental copy is done, then the container is resumed, then the backup is taken from the copy)
for stop mode, the backup will be taken directly from the volumes, no extra copy needed

note that if you select "snapshot" mode but your config doesn't support it, the backup will be downgraded to "suspend" mode - this will be visible in the backup log!

Hi Fabian

After some testing and stop mode seams to work without local storage.
We'll use that method for the time being since our storage don't support snapshot at the moment.

Thank you for the help