Hi everyone,

Using Xen-NG for couple of years but I am new to Xen Orchestra. And first of all thank you for this great software.

Considering moving partly away from my own written backups scripts I am currently playing around being particular interested in the XOA backup routines, in particular the CBT based delta backups. But maybe first the official facts about my setup:

Server: HP ProLiant DL380p Gen8
Xen-NG: 8.3 - fully patched
Xen Orchestra: self build - commit 9ed55 (as of today)
SR: 2 / both local ext / both are raid 10 disc based by the HPE Smart Array Gen8 Controllers
Remote: NFS mounted (Synology - Fully patched as of today)

Everything I tested so far works great. However I cannot get CBT based delta backups to run. I always get full backups and the error message is:

Can't do delta with this vdi, transfer will be a full
Can't do delta, will try to get a full stream

As said I am using an NFS based remote and all "normal" backups work like a charm. The Dummy VM I am testing to backup a newly set up Debian 12 (management tools installed) on the 2nd - non default- SR. CBT is enabled upon the disc as well in the the backup job ("Use NBD + CBT to transfer disk if available" enabled as well as "Purge snapshot data when using CBT "). I also enabled "Merge backups synchronously".

Unfortunately I do not really get my hands on this problem, because I do not find any particular error messages and do not really find good docs upon cbt. There are 2 observations I made:

• There are 2 *.cbtlog files in the SR directory of the VM. One showing 00000000-0000-0000-0000-000000000000 the other e011e9dd-e14b-4f0a-b143-092ea8f1b6a3. Is that normal?
• If I enable a memory including snapshot mode for each backup run there is one snapshot created in the default SR of the Host. These are not removed after the backup and remain orphaned. It looks to me these snapshots contain the memory (maybe this total BS - then please excuse this, but the observation might be helpful). However this problem is gone, if I switch to "offline snapshots".

Maybe I am just missing some stupid setting. Does anyone have any suggestion where to start troubleshoot.