Users Guide

8 Storage Solutions Guide
Disk Type
Virtual Hard Disk
A VHD is a file that resides on a formatted partition that the parent partition
has access to (see Figure 2). When presented to a VM, this file appears to the
guest OS as a hard disk with a set of raw blocks. The guest OS can utilize the
VHD just as it would a physical disk.
Figure 2. VMs Using VHD
Three types of VHDs (defined at VHD creation) are supported:
DYNAMICALLY EXPANDING — The VHD file grows as data is stored to the disk
with a maximum size not exceeding the size specified during creation.
Dynamically expanding is the default option when creating a new virtual
machine using the New Virtual Machine Wizard in Hyper-V Manager.
FIXED SIZE — The VHD file uses the full amount of space specified during
creation.
DIFFERENCING — The VHD file exists as a child disk in a parent/child
relationship with an existing VHD. The parent VHD is left intact and changes
that occur are stored on the child (differencing) VHD.
NOTE: For production environments, a fixed-size VHD is recommended based on
increased performance over dynamically-expanding and differencing disks.