CBT Breaking During Backup When VM Shutdown

[YouGotServered]

Hello forums! Two questions here.

1. I noticed that If I shut down a virtual machine while a backup is running, it seems like it breaks CBT. The next time I run the job with the VM on, Veeam has to read the whole VM and gives me with this lovely informational message: “CBT data is invalid, failing over to legacy incremental backup. No action is required, next job run should start using CBT again. If CBT data remains invalid, follow...". Is this normal behavior if the guest OS was shut down during a backup? No other changes were made to the VM. Obviously, application aware processing failed, but I can’t imagine why CBT would be affected by the guest OS VM power state.

2. I have noticed that after a CBT failure of some sort (such as the one above), it seems like CBT needs to be rebuilt for that VM in EVERY job it is a part of. For example, if I am replicating and backing up a VM whose CBT must be rebuilt, Veeam reads the whole VMDK for the backup job, and then again when the replication job runs later in the night. It was my understanding that a CBT map only needs to be built once per VM, but is it actually once per job (which actually makes more sense to me)?

Thanks!

[Gostev]

Hello Cory

1. No, this is not normal... or at least unexpected to me. I agree, nothing that happens in guest should affect CBT, unless there's some newly introduced regression on VMware side.

2. This, on the other hand, is normal. CBT is not being rebuild more than once, however after it has been reset, each job needs to read the entire VMDK to establish the baseline image state, from which it will start taking changes based on CBT data.

Thanks!

[YouGotServered]

Gostev, thanks for the quick reply.

1. I think I've seen this more than once, on more than one infrastructure. Most recently, this was 6.5 (not update 1 or 2, just 6.5). I'd be interested to see if anyone else can reproduce this behavior.

2. Understood, thanks!

[foggy]

Hi Cory, re: p.1 - can you confirm that you've shut down the guest OS properly, not just hit Power Off in vSphere Client? Thanks!

[YouGotServered]

Yes sir, and VMware Tools are up to date. Would shutting down vs powering off actually make a difference?

[foggy]

This was just an assumption that you could check in case it was power off.