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GabesVirtualWorld
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HELP! Replica job changes disk format

Post by GabesVirtualWorld » Jan 18, 2019 2:45 pm

Hi
Replicating a Hyper-V (SCVMM) VM from a 2012R2 cluster to a 2016 cluster, also changes the harddisk type from fixed to dynamic. This is highly unwanted because when I need to change the disks back afterwards, it will take a lot of downtime.

How can I prevent this change in disktype? And why in heavens name, does it even happen?

Gabrie

DGrinev
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Re: HELP! Replica job changes disk format

Post by DGrinev » Jan 18, 2019 2:57 pm 1 person likes this post

Hi Gabrie,

This behavior is expected and cannot be changed in the current version of the product.
We have it on the roadmap to change the said behavior in the future versions. Thanks!

foggy
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Re: HELP! Replica job changes disk format

Post by foggy » Jan 18, 2019 2:59 pm

Hi Gabrie, could you please tell why do you want to keep them fixed?

GabesVirtualWorld
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Re: HELP! Replica job changes disk format

Post by GabesVirtualWorld » Jan 18, 2019 3:22 pm

Hi,

The main reason we want to stay on fixed disks:
- We've discovered an UNMAP issue with our storage and dynamic disks on Hyper-V. Performance is heavily impacted when UNMAP is active.
- Our monitoring of the CSV volumes is currently based on fixed (and not growing) disks.
- For 1st line engineers it is quite a task to figure out if another VM can be added to a CSV when all VMs are thin.

Also a question for VEEAM: Why is the diskformat changed during a replication? Especially since it is nowhere to be found in the documentation that this change will happen and also the job creation wizard doesn't warn about this.

For the VMware Powershell cmd-let, there luckily is an option to force the disk type. But I also talked about this in the powershell section of the forum.

Can I use seeding to force the fixed format? Create first replica. Commit snapshot. Convert disk. Create new replication job and use the target as a seed?

Gabrie

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Re: HELP! Replica job changes disk format

Post by foggy » Jan 18, 2019 6:17 pm

Seeding might serve as a workaround, worth a try.

GabesVirtualWorld
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Re: HELP! Replica job changes disk format

Post by GabesVirtualWorld » Jan 18, 2019 7:10 pm 1 person likes this post

Nope, after making the first sync and committing the snapshot. I used that VEEAM as a seed and started a new replication. After the replication finished and removing the snapshot from the replica, I now have two VMs and both on dynamic disks. Quite a different behavior from VMware replication.

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Re: HELP! Replica job changes disk format

Post by foggy » Jan 21, 2019 3:36 pm

Do you mean the second VM was created when you mapped another job to replica with switched disk?

GabesVirtualWorld
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Re: HELP! Replica job changes disk format

Post by GabesVirtualWorld » Jan 21, 2019 6:51 pm 2 people like this post

I reran the test and I think I messed up in the first test. The second time it worked as expected.

Original- VM (fixed disks) --> Replication to ReplVM
ReplVM is dynamic with differencing disk (Snapshot).
Remove Replica Job.
Commit snapshot on ReplVM.
Convert ReplVM to fixed disk.

Then create new replication job to create replica from Original-VM to new VM and use ReplVM (with fixed disk) as replica (seed).

End result:
Original-VM = fixed
ReplVM = fixed with snapshots. Strangely enough the ReplVM was not renamed to the new suffix in the job, but kept the name of the mapped VM.
I then performed the final failover and I now have a running replicated VM with fixed disk.

Sadly though I do have some extra work with converting and then re-seeding, but for now it is a workable alternative.

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