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Sunday, July 12, 2009

Hyper V:-Pass-through disk

So, we have fixed disk, dynamic disk and differential disk in Virtual Server 2005. In Hyper V, we have another disk called "Pass-through disk". When should we use pass-through disk?

Let check it out...

Advantages of using Pass-through disk:-
a) Suitable for application which using high extensive I/O disk resources. (example: Sql server, Exchange Server, etc)
b) Direct access to the disk from inside a VM.
c) Allow to exceed 2TB VHD size limit

Disadvantages of using Pass-through disk
a) Cannot perform snapshot in the VM. (You can use hardware storage snapshot feature)
b) cannot use dynamic disk or differential disk

Step to configure pass-through disk:-
Use Disk Management snap-in to initialize first before use.
1. Select the disk, Right click -set to online.
2. Initialize the Disk and set to offline. (Do not create a volume/partition as it will be accomplished inside the virtual machine).

*Pass-through disk must set to Offline.

To use pass-through disk in a Guest, you must select Attach a virtual hard disk later in the New Virtual Machine Wizard.

After finish the New Virtual Machine Wizard, edit the setting of the Guest VM. Pls refer to below diagram and select physical disk.

In Failover clustering, the storage will no show any drive letter for pass-through storage.

Due to Pass-through disk did not has NTFS partition, you cannot add into Cluster Shared Volumes. We will discuss more in my next article.

-The VM Configuration file must store in different LUN.
-To boot a virtual machine guest operating system, it must attached to a virtual IDE controller.
Virtual SCSI controller work when Integration Services is installed.

Lastly, if you want the VM to directly access the physical storage, pls use pass-through disk.