A: Physical hard drives break up their data by blocks, and virtual machines (VMs) do the same. When a VM's partitioning of those blocks doesn't match the partition boundaries on the host, the virtual disk is considered misaligned. That misalignment inappropriately overlays the virtual disk's blocks atop the host's physical blocks, forcing more physical blocks to be read from or written to than should be necessary.

New virtual disks can be created with the proper alignment using the Windows diskpart command. First, boot the VM into a version of WinPE that includes support for a command prompt. Then enter the following commands to create an aligned partition:

diskpart
list disk
select disk <diskNumber>
create partition primary align=32
exit

Once the aligned partition has been created, you can format the disk normally.