Search This Blog

Tuesday, April 9, 2013

Is Live Migration Supported Pass Through Disk in Windows Server 2012 Hyper-V?


haha…this question is a bit tricky. Well, just heard news from here (has taken out), that pass-through disk is “NO” longer supported in live migration operation.

[Updated]- 12 April 2013

The answer is “Yes”. It is still supported after confirmation from Hyper-V Product product group, Redmond

For those of you who are not familiar with “Pass-thorough” disk, let me give a do a bit of explanation.

Pass through disk is also known as raw disk. It is exactly like a LUN that we present directly to the VM. Well, in term of performance is still consider the best among all different types of disk (fixed, dynamic or differencing disk) but it did came with a limitation : Portability. You cannot export or easily move the disk to another Hyper-V host. We often use this disk when our VM require more than 2TB of hard disk size. But with Windows Server 2012, we can now relies on VHDX (support up to 64TB) and fixed disk has almost the same performance as pass through disk. Refer to below comparison and additional whitepaper on Virtual Hard Disk Performance.

Compare the physical disk vs fixed disk. Both disk performance is almost identical.

So, when design your implementation, please don’t use Pass Through Disk but choose fixed disk if you would like to do live migration

Relevant post:


  1. Hi, are pass-through disks supported with Live Migration in Windows Server 2012 Hyper-V for linux e.g. SLES guests?

  2. Hi,
    Yes if it failed under supported guest OS list. If pass through disk reside on stand alone host and between different clusters, then it is not supported. You can refer to supported list here:-