interferance between tape backup and VM

[davlaw]

I get an occasional error such as the following

2021-06-02T03:14:47-04:00: backup snapshot vm/117/2021-06-01T00:00:15Z 2021-06-02T03:15:03-04:00: TASK ERROR: store 'pbspsiscsi', unable to load chunk '4ddfecd9ad1d749184e4bac5592f3506a7bfb107706778a68ed006b22fd61d18' - blob too small (0 bytes).

Almost always different, but my concern is the snapshot of the vm and tape backup are interfering with each other and why might I be hitting this condition

proxmox-backup: 1.0-4 (running kernel: 5.4.114-1-pve)
proxmox-backup-server: 1.1.9-1 (running version: 1.1.9)
pve-kernel-5.4: 6.4-2
pve-kernel-helper: 6.4-2
pve-kernel-5.4.114-1-pve: 5.4.114-1
pve-kernel-5.4.106-1-pve: 5.4.106-1
pve-kernel-5.4.65-1-pve: 5.4.65-1
ifupdown2: 3.0.0-1+pve3
libjs-extjs: 6.0.1-10
proxmox-backup-docs: 1.1.9-1
proxmox-backup-client: 1.1.9-1
proxmox-mini-journalreader: 1.1-1
proxmox-widget-toolkit: 2.5-6
pve-xtermjs: 4.7.0-3
smartmontools: 7.2-pve2
zfsutils-linux: 2.0.4-pve1

 

[dcsapak]

does that chunk exist? does that snapshot exist ?

 

[davlaw]

hate to answer this with a "I don't know"

I have my prune set every 30 mins, maybe it was there at the beginning of the backup but later was purged during the backup

Garbage collection 1x a week.

Or, I have seen failed snapshots appear, and I later cleared. Maybe these?

I have a feeling that cleaning failed snaps and good clean garbage collection without error , will make this better

I was just trying to get a idea of the logic used as the datastore is rather dynamic and slow hardware(older)/interfaces

 

[dcsapak]

so it seems that there is wrong locking behaviour when pruning, so it can happen that pruning deletes a snapshot while it was being used
i sent a fix to pbs-devel ( https://lists.proxmox.com/pipermail/pbs-devel/2021-June/003371.html pending review)
so that in the future this should not happen

prune job should instead then warn and continue and not delete the snapshot

 

[davlaw]

Great glad I was able to help