CBT: the thread to centralize your feedback

olivierlambert

I'm not aware of such issues (at least now) (doesn't mean it doesn't exist more broadly but it's the first report). We'll upgrade our own production to 8.3 relatively soon, so it will be the opportunity to also check internally.

rtjdamen

@olivierlambert ok, maybe u experience some differences as well, we were on 8.3 since February and did patch last friday, since the patching is see a decrease.

What i believe is happening is that GC processes are blocking other storage operations. So only if a coalece is done on an sr i see multiple actions like destroy, enable cbt and change block calculations being processed. As far as i know this was not the case before, they also could take some longer but it was not related to (or i have never noticed it).

Maybe we can confirm if this behavior is by design or not?

olivierlambert

I'm not sure there's a change related to that but I can ask @Team-Storage

rtjdamen

Anyone else experiencing this issue?
https://github.com/vatesfr/xen-orchestra/issues/8713

it's a long time bug that i believe is pretty easy to fix and get CBT backups to get more robust. Would be great if this can be implemented!

olivierlambert

Pinging @florent about this

florent

@olivierlambert yes the fix is in the pipeline (on xapi side )
it won't migrate a snapshot with cbt enabled, and won't allow to disable cbt on a snapshot

olivierlambert

Thanks!

rtjdamen

@florent so not an option solving this inside xoa? Could be usefull for the short term.

rtjdamen

Support found that automatic refresh of our sr every 30 seconds delayed this. It seems we had this for a longer time but now it’s more aggressive. Disabled this as this is not required. This resolves our issue here.

olivierlambert

Wow, rescan every 30sec? I thought the default value was 10 min or something Do you remember setting it manually at some point?

rtjdamen

@olivierlambert No never changed it. From what i understand from Jon it's default this where his words "and all these SRs have auto-scan enabled. This means every 30 seconds, the pool master will scan the entirety of every SR". We changed this and the problem is gone.

olivierlambert

Okay, I thought the autoscan was only for like 10 minutes or so, but hey I'm not deep down in the stack anymore

gb.123

Hello,

Just a feedback. I am having trouble using CBT Backups with NBD.
Host Details:
XCP-NG Version : 8.3 latest (stable)
Xen Orchestra: latest:stable (From Source)

The first full backup always seems to work. The delta backup gives the error: 'HANDLE_INVALID'

the writer IncrementalXapiWriter has failed the step writer.checkBaseVdis() with error HANDLE_INVALID(VBD, OpaqueRef:xxxxx). It won't be used anymore in this job execution.
Start: 2026-08-09 14:01
End: 2026-08-09 14:01
Duration: a few seconds
Error: HANDLE_INVALID(VBD, OpaqueRef:xxxxxx)
This is a XenServer/XCP-ng error