Version 8 Update 2A

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Version 8 Update 2A

Veeam Logoby jb1095 » Wed Jun 10, 2015 2:17 pm

We would like to turn off CBT so our next backup is not a full backup after we increase our vmdk size. In the release it states that we can do this by editing the registry. We want to make sure that if we do this, we do not run into any issues and that we do not do a full backup, or at the very least a full backup of the one disk we changed.

In other words, what should we expect if we make this change specifically after increasing the size of one of the disks my 50 GB. We are on VSphere 5.5 update 2D. Thanks
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Re: Version 8 Update 2A

Veeam Logoby foggy » Wed Jun 10, 2015 2:21 pm

Jon, if your hosts are patched against the VMware CBT issue, you can upgrade to Veeam B&R v8 Update 2a 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. You incremental backups will continue to run normally.
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Re: Version 8 Update 2A

Veeam Logoby jb1095 » Wed Jun 10, 2015 2:24 pm

Our hosts are patched and we are on Update 2a now. Keep in mind, we just want to increase the space on one of our drives and are hoping to avoid a full backup as a result. Is this the case if we do the CBT registry change? Also, would we be required to reboot the Veeam server after making this registry edit?
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Re: Version 8 Update 2A

Veeam Logoby foggy » Wed Jun 10, 2015 2:48 pm

CBT for the entire VM will not be reset, however, the disk still needs to be read entirely after resize to get the changes for transfer. Yes, Veeam B&R server reboot will be required.
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Re: Version 8 Update 2A

Veeam Logoby jb1095 » Wed Jun 10, 2015 6:25 pm

foggy,

Thanks so much for the prompt responses. We made the change to the registry and tried increasing the size of a test VM. While the second backup does indeed show the disk size was increased(from 10GB to 20GB). Veeam still reports that it only read 10GB of that disk and we don't think that looks right. This is the message we get when Veeam backs up the VM(for this particular disk).

Hard Disk 2(20.0 GB) 10.0 GB read at 50 MB/s[CBT].

Shouldn't it be reading 20GB and not 10GB if this is a 20 GB disk? FYI, the disk in question is thick provisioned.
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Re: Version 8 Update 2A

Veeam Logoby Gostev » Wed Jun 10, 2015 9:52 pm

There is simply no point to read the remaining 10GB, as they are empty. vSphere too knows that they are still empty, as VM did not attempt to write there yet - and tells us this through the CBT query that we issue when doing a full backup. Thanks!
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