Changed VMDK size, ALL disks read again?

[loelly]

So I'm on ESXi 5.5U2 and Veeam 8 Patch 1. We've some huge file servers with a couple of disks. Yesterday someone had the need to resize one VMDK (1.7 TB -> 1.9 TB). I would have expected CBT to reset and Veeam to re-read this single disk. But instead, Veeam tried to read ALL disks (~7 TB of data). Why is that?

[foggy]

Maik, this is expected, CBT is reset for the entire VM. However, if your hosts are patched against the CBT issue, you can upgrade to Veeam B&R v8 Update 2 and disable automatic CBT reset. For that, create the ResetCBTOnDiskResize (DWORD) registry value under HKLM\SOFTWARE\Veeam\Veeam Backup and Replication and set it to 0.

[loelly]

Wasn't it just reset for the VMDK which was resized in earlier releases of Veeam?

[foggy]

I believe the workaround implemented both in hotfix for Veeam B&R v7 Update 4 and in Veeam B&R v8 was similar - CBT was reset for the entire VM.

[loelly]

Do I really need to be on Veeam 8 Patch *2*? I'm on patch 1 and running vSphere 5.5 U2.

[foggy]

The mentioned registry value was added in Update 2.

[loelly]

Thank you Alexander!