If I enable ABM at the vCenter level, I'm guessing this applies ABM on all VMs connected to the vCenter server. How does this handle Linux VMs? I know that it only works on NTFS drives so if it detects that the VM is running something other than NTFS, does it just keep using CBT and not apply ABM?
Or if I have a mixture of VMs should I enable it on a per VM basis?
Yes. Enabling ABM at the vCenter level applies to all VMs (unless you manually disable it per VM, overriding the host setting). Since only NTFS is supported ABM cannot detect any information about the linux file systems and hence won't do anything. It shouldn't cause any issues, it's just the core checking the file system of the volume and then not doing anything further once it is not NTFS.
To be clear, ABM does not replace CBT. CBT is still the primary method used to track changes, it's just augmented by ABM. ABM detects the active blocks. CBT detects the changed blocks. Combine the two and RR only backs up the changed active blocks. If ABM isn't enabled or doesn't support that file system then RR backs up all the changed blocks. You still get valid, usable backups via CBT, you just don't get the benefits of ABM.
Yes. Enabling ABM at the vCenter level applies to all VMs (unless you manually disable it per VM, overriding the host setting). Since only NTFS is supported ABM cannot detect any information about the linux file systems and hence won't do anything. It shouldn't cause any issues, it's just the core checking the file system of the volume and then not doing anything further once it is not NTFS.
To be clear, ABM does not replace CBT. CBT is still the primary method used to track changes, it's just augmented by ABM. ABM detects the active blocks. CBT detects the changed blocks. Combine the two and RR only backs up the changed active blocks. If ABM isn't enabled or doesn't support that file system then RR backs up all the changed blocks. You still get valid, usable backups via CBT, you just don't get the benefits of ABM.
Ahh okay thank you for the clarification. The documentation wasn't clear on how it handles non NTFS VMs. I'm guessing it would be foolish to have it screw up a VM if it was enabled but not using NTFS.
Also, good to know about CBT + ABM.
Are there any use cases where you shouldn't enable ABM?
I cannot think of any cases where you wouldn't want ABM enabled. Perhaps a really big volume with trillions of files? Even then if you don't have many exclusions it may impact backup speed. That's purely speculation though. It may work totally fine and not impact things at all.
Thanks again. Oddly enough, I was able to enable it on one cluster but on another cluster whenever I click Apply Changes, the checkmark disappears and setting goes back to No. Maybe I need to reboot the core.
Was this cluster protected and then you upgraded to 6.3? If so, we've found a defect related to enabling ABM at the cluster level. The core won't let you do it. So you have to enable at the VM level. We're working on a fix, but it's gonna take some time. So far we haven't found any workarounds other than enabling ABM on a per VM basis.
Yes it was however this was the case for both clusters (and I'm enabling ABM at the vCenter level). We have two RR Cores both pointing to the same vCenter but each backing up different VMs.
Hold on a sec - I had to redo protection on the one core that worked because we were experiencing a different bug which has since been corrected. That's why it worked on one and not the other. Clearly the bug you referenced.
