Xen (ABD) backup fails with "there were no servers available to complete the specified operation"

If you run a backup of a Xen VM using the ABD method, and job fails with the message:

There were no servers available to complete the specified operation.

Error processing VM: XT Returned 1

Then is this means that your ABD is not ready. The following root causes could be at play:

1. The ABD is assigned to an SR that is disabled or no longer available
2. The ABD has a network that is no longer valid
3. The ABD cannot be booted because there is not enough memory on the Xen host
4. The ABD cannot be provisioned from the template because there is not enough storage on the SR
5. You are running the ABD on a pool with more than one host, but no no shared storage

Check ALL of the above carefully before proceeding. Make sure 1-5 are FULLY corrected before proceeding after that:

1. Enable "view hidden objects" in XenCenter. Power off and delete all ABDs on the affected host. DO NOT DELETE templates.
2. Try to run an ABD diagnostic job.
3. If it fails, change the network of the ABD in the ABD settings page and then repeat steps from 1.
4. If 3 fails, delete the ABD template from the affected Xen host. Repeat from step 1.