Ah yes the oldie but goldie that is resizing replicated disks.


So the way round this is covered in various places


So what I did was:

  • Pause replication
  • Log onto the host the VM is replicated to at the DR site
  • I went to its datastore and renamed the folder with a -bak extension. You have to do this so that when you disable replication it does not delete the actual files at the DR site. Otherwise  you’d have to start replication from the beginning again, as you would have lost your seed!
  • You then disable replication, you will see the following error which is totally normal, because remember we renamed the folder at the DR site to stop it from being removed:vsphere_replication_disk2

So once you have done that, you can then increase the size of the disk at the Protected Site like you normally would by editing the VM settings. Then  the key part is, you then login to the host at the DR site, navigate to the datastore where the renamed folder is. You then run:

vmkfstools -X size vmdk

For example:

vmkfstools -X 50G Test-VM.vmdk

so in my case the disk was originally 550GB and had been extended by 50Gb to 600GB, so what I had to do here is increase the size of the vmdk files here to 600GB

vmkfstools -X 600GB servername_1.vmdk


Then once that has been done you rename the folder at the DR site back to what it was originally called.

Then you reconfigure replication at the source, and point it to the folder at the DR site, you will then be asked if you want it to seed, click yes.

Then what it will do is a compare and just send over the link the differences saving you a chunk of b/w!

Its a shame the process of extending a vmdk of a VM that is protected by vSphere Replication, is that complex.

You would hope that after all this time, it would have been simplified, but hey such is life!



There is another way you can resize a vSphere Replicated VM…that most people do not seem to be aware of:

Resize Virtual Machine Disk Files of a Replication that Does Not Use Replication Seeds

Basically you:

  • Run a planned migration
  • Stop replication
  • Resize the original source VM and then resize the recover VM (which is powered off)
  • Remove the recovered VM at the recovery site from the vCenter inventory (remove from inventory NOT delete from disk!)
  • Reconfigure replication and now use the recovery site VM as a seed




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