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jonhsykes
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Discover which VMs/VHDs don't have CBT?

Post by jonhsykes » May 19, 2017 5:32 pm

Is there a way to discover VM replicas that don't have CBT through PowerShell script or some other mechanism?

jonhsykes
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Re: Discover which VMs/VHDs don't have CBT?

Post by jonhsykes » May 26, 2017 1:06 pm

bump

Gostev
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Re: Discover which VMs/VHDs don't have CBT?

Post by Gostev » May 26, 2017 7:55 pm

For VMware or Hyper-V? Your question is confusing because CBT is a VMware thing (Hyper-V uses RCT), but VHD is a Hyper-V thing (VMware uses VMDK).

jonhsykes
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Re: Discover which VMs/VHDs don't have CBT?

Post by jonhsykes » May 26, 2017 9:01 pm

Hyper-V 2012 R2. I know the files are stored on Hyper-V hosts, however it would be nice if there was a reporting mechanism inside of VEEAM to use for this scenario to report on the VMs that don't have CBT (ie wont use incremental replication for next replication cycle). It's helpful for large data center migrations
https://helpcenter.veeam.com/docs/backu ... tml?ver=95

vClintWyckoff
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Re: Discover which VMs/VHDs don't have CBT?

Post by vClintWyckoff » May 26, 2017 9:26 pm 1 person likes this post

Just to reiterate there is no native change block tracking in Hyper-V on 2012R2, so Veeam uses a filter driver that gets installed on the actual Hyper-V hosts to track the changes since the previous backup. In the rare cases where there is issues with either CBT on vSphere or in your case the filter driver on Hyper-V, VBR will read each block to determine whether or not its changed since the previous backup. So in any case you're left with an incremental backup.

As stated in the link you posted above...
CBT is enabled by default. You can disable it either at the host level or at the job level for troubleshooting purposes. Note that if you choose to run incremental jobs with CBT disabled, the backup window may increase dramatically, as Veeam Backup & Replication will read all VM data to detect what blocks have changed since the last job session.
However, as Anton mentioned RCT (Resilient Change Tracking) is available in Hyper-v 2016 making the filter driver no longer required. Hope this helps.

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