Backup to PBS very long due to missing dirty bitmap

[Jackobli]

Hi guys
I know there are many threads about, but I haven't found the right one who explains my question perhaps.
How is the behavior or where do I find the documentation of PVE for handling the "dirty blocks bitmap" for doing incremental backups?
We know:

• If a VM has been stopped, the Bitmap is deleted
• But there must be other cases…

Yesterday one of my VM suddenly had it lost and says:
scsi0: dirty-bitmap status: created new
Sometimes we also see "scsi0: dirty-bitmap status: invalid created new"
These VM hadn't been stopped. Also a migration usually keeps the bitmap.

Usually that is no big issue, but on very large disks the backup needs very long and all other backups (on that node) are stalled until this one is done.

Our storage backend is ceph

Regards, Urs

 

[aaron]

The two main cases where the dirty bitmap is currently lost:
- VM had seen a full stop. This is also the case if you use the "Reboot" option from the Proxmox VE UI to apply pending changes
- The VM is backed up to more than one Backup Server, as the dirty bitmap is bound to a target Backup Server.

 

[spirit]

also, if the verify job on pbs is detecting error on backup, the dirty bitmap is lost to do a new full read.

 

[Jackobli]

Thank you, both (aaron & spirit).
I don't think, that one of the three actions did occur. The vm has an uptime of 8 days and the backup that did start from scratch was yesterday. We only backup to one server / namespace. And the last verify (yesterday at 10am) has ended without any errors.
IMHO, this happens with some of our VMs with disks larger than 1 TB every once in a while.
Regards, Urs