Shrink required prior to backup of dynamic volume

[tjrgsa]

Case ID: 05042081

Hello Everyone,

I actually figured out an acceptable workaround to my problem but the rep suggested I post my findings here as well.

I ran into an issue when trying to do a bare metal restore of a dynamic disk to the same hardware. I'm new to Veeam and have an experimental server (Windows Server 2019) that I was using to try out the product. I have a couple of NVMe drives that I want to mirror which contain the OS, and although it's not my area of expertise my understanding is that in this particular case a hardware controller isn't the way to go. So, I setup the mirror in Windows' disk management and wanted to simply try backing up the server as-is and restoring it to the exact same hardware ("Entire Computer" backup mode). No virtual machines yet, just physical.

Well, the backup worked fine but the restore failed. I did a diskpart clean on the disk beforehand and converted it to GPT. Then I loaded from the rescue media and the auto-map failed with the error "Unable to auto-match disks, please use manual restore mode". So, I went into manual mode but when I tried to customize the disk mappings by right-clicking the whole disk and choosing "Apply Backup Layout", I got the error message "Insufficient Disk Size". Next, I tried to click the unallocated space and drop in the partitions 1-by-1. First the Recovery, then the EFI, then the main C: (dynamic) volume. Recovery and EFI were fine, but when I tried to add the C: volume I got the prompt "This volume is larger than the specified destination. Shrink the volume to fit the destination?" I tell it yes but at this point I'm thinking there's some sort of a slight sizing mismatch since all I'm doing is restoring to the exact same hardware as where I took the backup. They should match I would think. I proceed with the restore but it fails with the error "Resizing (C:) Error: Asynchronous execution of the 'volume shrink' has failed. COM error: Code 0x8004257." The rep said that this corresponds to Microsoft's error "The specified shrink size is less than the minimum shrink size allowed."

When I reinstall but don't mirror the drives, leaving them as "basic" disks, then following the exact same procedure does the restore without a problem. So, the volume being dynamic has to be the main issue here.

Next, I reinstalled again and added the mirror, but I preemptively shrunk the C: volume by 100MB BEFORE doing the backup so it would give Veeam a little more unallocated space to work with during the restore. Sure enough, that did the trick. The auto-map process worked as well. Both drives remained bootable after the restore and the data was as I expected it to be. I'm just puzzled as to why the shrink was needed.

I could be wrong but I can't help but think that either Veeam is making the size of the dynamic C: volume slightly too large during the backup, or it's partitioning Recovery and EFI in such a way that doesn't leave enough room on the disk for C: during the restore.

Regardless, I'm fine with the workaround as it was easy enough to just add the command that does the shrink to my script that sets up the disks. If there's an explanation as to why the shrink is necessary though, I'm all ears.

Either way, hopefully this info might help someone who has a similar problem in the future.

Thanks!

Tom

[Dima P.]

Hello Tom,

The dynamic volume resize during Bare Metal Recovery is super tricky and I'd say that the best way to perform the recovery in such case is to follow the approach you've described. Glad you nailed it and thank you for your post!