Don't block VHD backup if CBT doesn't exist

[olivierlambert]

Are you using XOA or XO from the sources?

both

Which release channel?

both

Provide your commit number

No response

Describe the bug

Some old XS doesn't support CBT at all. It's not a big deal since we can still use regular VHD diff. However, the fact CBT is absent shouldn't break the "legacy" VHD export, eg if there's no NBD network nor any CBT backup enabled.

If it's not too hard to be more robust in this case then it might worth it.

Source: https://xcp-ng.org/forum/topic/9443/getting-message_method_unknown-vdi-get_cbt_enabled-with-xenserver-7-1

Error message

`MESSAGE_METHOD_UNKNOWN(VDI.get_cbt_enabled`

To reproduce

1. Go to '...'
2. Click on '...'
3. Scroll down to '...'
4. See error

Expected behavior

No response

Screenshots

No response

Node

20

Hypervisor

XenServer 7.1

Additional context

No response

[lukkri]

I confirm that. I use XOA from sources. Error is only on XenServer 7.1LTS, but only with delta backup. I have tried 2 commit number - 7b8a4e7 and latest master with same bug. For now I have setup a full backup of VMs until the problem will be fixed. Next XCP-NG 8.2LTS works without problem.

[bberndt]

I confirmed this too, with Delta Backup. Never tried the full one. What worked for me, was upgrading the host to XCP-ng 7.6 (as far as I can go right now)

-Sidenote, the update repos don't work. I assume because CentOS 7 is gone?

I was getting the same error right away when running the backup task manually, or scheduled. Running it manually now, seems to work, its transferring a disk now, at least.

Xen Orchestra, commit [cb6cf]
Master, commit [4d768]
from https://github.com/ronivay/XenOrchestraInstallerUpdater

I'd have to check, it might be one of my last hosts on Citrix 7.1. The XCP-ng 8 branch breaks the RAID card monitor software from Broadcom/ LSI/ Avaya/ 3Ware for a card we used a lot of...