Andrew Fryer, my team mate and fellow IT Pro evangelist has posted a great article on why he likes VHDs. I have to agree with him and I’ll add something else…
VHDs are a file based format as opposed to the traditional sector based format. This is very cool because it allows “offline servicing” for the OS, which means that you can service the VHD without it being booted. This is cool because say you have a demo environment and you want to update a driver all you do is mount the VHD and use DISM like this:
DISM /Image:V:\ /Add-Driver /Driver:M:\Drivers /recurse
to add the driver, then on next boot it’s done. Simples.
More complicated is what’s going on under the hood, but essentially a VHD will consume less disk space than the same disk in a sector based format as each unique file is only stored once in the VHD format.
Throw your brilliant VHD tips our way in the comments…
another cool thing to do if you have a blade center and a netapp. create a boot lun and install a vhd to it. sysprep it flexclone it then present to another blade, instant install! Its true you could just flex clone the boot lun but whats the fun in that. For superfast p2v of a old school bootable lun, flexclone the bootable lun and present to your hyper-v server run disk2vhd against that and configure hyper-v to use the resultant vhd file! this is extremely fast compared to scvmm or other p2v tools.
Very nice rapid deployment idea.... I actually do something similar, I keep a basic demo OS ready to go then I just copy the VHD, poke a couple of bits into it and voila, it's done.