Are your source systems using local disk for swap? Vmotion might  be trying to create vswap on the datastore. Normally in this config (you set loacl swap option) it will try and find a local vmfs on the target host and relocate the local swap file there. If it can't do that I beleive it then tries to locate the swap file with the vmx file.

dB

We have tried to reproduce it here and did not see a new file created. Could be a special condition that is causing this. Are you monitoring the datastore while the vmotion is taking place. I'd be interested to see what you see, presumably for a period there are two vswap files present? Could you post a couple of screen shots?

dB

that's weird.... but interesting though.

Duncan

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Maybe this has something to do with the changed behaviour of the .vswp

file under vSphere?

i.e. it's created on power-on and deleted when powered down.

Hi,

Thanks for the information. But how do you mean, a target host is pressured?

Does it deny a VMotion in case an ESX Host is already overcommited? (and is the function of creating this file to maybe check some things?)

I want the technicall stuff

Next to that, you are saying it's thin provisioned. But imagine the following scenario:

I've got an ESX Cluster with many VM's. The situation could occur in where 8 VM's are being VMotioned at the same time (same datastore).

Now these VM's all carry 8 GB memory which is totally used inside the guest. In that case I need 64 GB of very temporary space available in my datastore, right?

If so this all could result in a new math to calculate the datastore size.

Thanks so far!

Kenneth van Ditmarsch

So as far as I know you can only have two concurrent vmotions in flight at any one time. The other thing is that the temp swap will only be used for activity as the machine transistions so should not grow to the size of the memory. If you du the file systems you should see the the dick blocks being consumed. Engineers think this should be tops 400M even if it is used at all. By pressured we mean the amount of memory free is low. That will not deny the VM to vmotion unless we can't allocate enough reserved memory (this is zero by default). Once the transition is complete the VM reverts to the orginal swap file and the temp is deleted.