Changed VMDK size, ALL disks read again?

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Changed VMDK size, ALL disks read again?

Veeam Logoby loelly » Tue May 12, 2015 8:53 am

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?
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Re: Changed VMDK size, ALL disks read again?

Veeam Logoby foggy » Tue May 12, 2015 10:11 am

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.
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Re: Changed VMDK size, ALL disks read again?

Veeam Logoby loelly » Tue May 12, 2015 10:29 am

Wasn't it just reset for the VMDK which was resized in earlier releases of Veeam?
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Re: Changed VMDK size, ALL disks read again?

Veeam Logoby foggy » Tue May 12, 2015 11:25 am

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.
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Re: Changed VMDK size, ALL disks read again?

Veeam Logoby loelly » Tue May 12, 2015 3:10 pm

Do I really need to be on Veeam 8 Patch *2*? I'm on patch 1 and running vSphere 5.5 U2.
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Re: Changed VMDK size, ALL disks read again?

Veeam Logoby foggy » Tue May 12, 2015 3:12 pm 1 person likes this post

The mentioned registry value was added in Update 2.
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Re: Changed VMDK size, ALL disks read again?

Veeam Logoby loelly » Tue May 12, 2015 3:17 pm

Thank you Alexander!
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