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vm replication not happening incrementally

Beginner
Posts: 8
Comments: 10

Hello all

I have had a few problems with the replication of an SQL Virtual Machine, the VM has a virtual hard drive of 250gb and approximately 100gb is in use.

It initially ran for about 5 hours and would fail at the end, so I renamed the replica folder, forcing it to replicate from new - this was successful and replicated the whole 250gb in about 4 hours.

But subsequent replications are transferring 120gb every time even though CBT Replication is selected in the options and also the Provisioning Mode is on the default of thin.

Stepping through the logs I see entries for 'Changed Block Tracking (CBT) is enabled' and 'Changed Block Tracking (CBT) is used' but these do not seem like incremental replications to me.

Does CBT on an SQL VM Replication even work?

I can verify it does work on a Primary and a Copy (2nd Location) back, so the replication is a bit puzzling.

 

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Posts: 22
Comments: 2659

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Hi,

As far as I can see from the near thread, you've already found my recommendations there - resetting CBT on the original backed up VM should do the trick. In your case it looks like CBT reports the whole disk area instead of incremental changes, which is why it's successful in logs, but the actual traffic is huge.

Thank you.