Disclaimer: This solution may not be suitable for your environment. Please read through the whole post before attempting to perform the following steps in your environment.
One of the best benefits of a virtualized server is increasing its disk space in a flash. I ran into an issue with my Veeam replication job which replicates said server with expanded disk to our secondary site. Ever since expanding the disk, all future replication jobs were failing for that specific VM.
Once Veeam begins reading the disk it compares the source VM with the destination replica. It then it finds that the disks are not the same.
To resolve this, open the snapshot manager of the replica VM. All the snapshots will have to be consolidated. This is the biggest drawback. It’s either, recreate the replication job or consolidate your snapshots. You’ll lose your restore points. Select the latest snapshot and click on Delete All.
Since this replica doesn’t have the same disk size as the source VM we will have to modify that to reflect those changes. Right click on the replica VM and click on Edit Settings.
Make sure you select the correct Hard disk and increase the provisioned size to exactly the same size as the source VM disk. For example, if my source VM Hard disk 1 was increased from 250 to 325 (which caused the replication job to fail), then on the replica I will do the same.
Go back to Veeam, right click the replication job and click Edit. Because we consolidated the replica’s snapshots and modified the replica hard disk, we will need to map the replication job’s source VM to the replica we just modified.
On the first screen, enable “Low connection bandwidth (enable replica seeding)”
Seeding will appear on the left side of the window.
Click Next until you are in the seeding section. Enable “Map replicas to existing VMs” under “Replica Mapping.” Remove any VMs that are not affected. This step will not delete anything. It just removes the VM from mapping to an existing replica VM. Then click Detect. In the Replica VM column you should see the source VM name populate suffixed with “_replica”. Finish the settings and then retry your replication job.
If everything goes smoothly, Veeam will read the source disk and match it with the replica’s disk. Veeam will attempt to align the data blocks. Because we modified the replica’s disk, change block tracking will not be enabled. This process will take a while depending on how much data needs to be transferred over but hopefully you see a successful job.
Future replication jobs will now be successful and CBT should be enabled.
Kudos to Veeam Support, especially Phil Ambro. He provided me with the solution and educated me on how Veeam’s processes. Veeam has the best customer service around. Each time I call they always surprise me with the amount of knowledge each support person has.