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kinsden
Enthusiast
Enthusiast

VMotion and snapshots

Hi All,

I am trying to migrate one of my VM (having a few snapshots). Both the source and destination ESX hosts are similar hardware type and attached to the same FC SAN.

When I try to VMotion this VM and select the destination host in 'Migrate VM Wizard' it gives a warning in 'Compatibility' pane saying 'Reverting to snapshot would generate error (warnings) on the destination host'. I tried VMotion'ing another VM which does not have any snapshot taken and it didn't give this warning. I also tried to go for cold-migration for the problem VM, but same warning !!!

Does anyone know what does this mean? And what's the way to make it work?

Cheers,

Kinnar

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11 Replies
chandlm
Expert
Expert

Did the migration actually fail? I don't believe the warning will stop the migration from actually happening. I haven't seen any issues with doing those types of migrations personally.

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Chamon
Commander
Commander

I think it is warning you that if you don't get rid of the snapshots before you move the vm when you try to revert to it later it may not work or it will just generate other warnings. Why this is I am not sure. There may be information in the files that tell the vm where its snapshot resides that is not updated during the vmotion. Do you still need the snapshots?

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chandlm
Expert
Expert

It shouldn't need to modify a location of the snapshot files since the VMotion wouldn't move them anyway right? I'm relatively sure that I've gone back to snapshots on VMs that have been through VMotion operations without issue but if I get a chance I'll verify that later.

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Chamon
Commander
Commander

That is true. I guess I was thinking of moving the VM to a different LUN not

Vmotion. Sorry about that. And it is a warning about generating a warning on

the Host. The vmotion does not error out.

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kinsden
Enthusiast
Enthusiast

Hi,

I haven't gone ahead with the migration because this VM is our VirtualCentre. But I will give it a go as its just a test environment. Will post back my results. Cheers for your help, chaps!!

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PeWe1201
Contributor
Contributor

Hi,

this is a normal behavior.

Because this is only one of the problems depending on Snapshots I normaly use the Snapsuot Feature only as part of the Change Process.

I tahe a Snapshot, do the Change, make shure, that the Change will be successfull, and then delete the Snapshot imeadiatly.

Very often I had the Problem, that a running Machine with a Snapshot will go into a BlueScreen (Windows) after doing a Migration.

If I delete the Snapshot before migrating this Maschines, this will work fine!

Therfore I will recommend you to first delete the Snapshot, and than do the Migration.

Peter

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chandlm
Expert
Expert

Interesting, I have never had that happen to me (yet). Do you see the bluescreen during, immediately after, or some time later?

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kinsden
Enthusiast
Enthusiast

Hello chaps,

I was able to VMotion this VM and it did not give any errors. The reason I am posting back the results this late is I wanted to make sure that the VM (having VC) keeps on running properly and it does. So looks like VMotion'ing VM with snapshots work! But there may be cases where it may not work (like in PeWe1201's case) and so I would use snapshots ONLY when required and then delete them.

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Chamon
Commander
Commander

We had an Engineer from VMware here this morning and what he told me that he

has seen is the following. That after a VM has been Vmotioned somewhere and

you want to revert back to a snapshot this process may error out. If it does

the VM needs to be rebooted and then the process of reverting back to a

snapshot will work.

lholling
Expert
Expert

From my understanding the thing you are doing is reverting the snapshot possibly including memory (if you snapshotted memory as well) back to a point in time which means that it could have been using a particular architecture feature that may not be on the "new" server that you are VMotioning to if you revert the Snapshot.

Leonard...

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HMC-Frank
Contributor
Contributor

lholling is correct. If you vmotion from a four socket dual core to a two socket quad core, but you had cpu affinity set to physical cpu/socket three before vmotion and that was also set in your snapshots, when you revert back using the snapshot on the new host and your vm is looking for physical cpu three, it is not there, only two sockets. The reason the VM worked was because during vmotion the cpu affinity got dumped (default behavior).

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