One thing I'd recommend doing is running sysprep on the
base image to make sure the SIDs are unique for your
virtual pcs.
Thanks for the tip Phil.
TIP: Once you are happy with the base disk, you can make
it read-only so that you don't change it by mistake.
THE BAD:
The one thing I've discovered using them that irritates
me is that the various security updates are so fast and
furious that the original base disk becomes alomst
useless over time. So sometimes, if I just want to set
up a quickie virutual box and don't need Internet
access, I'll just set it up from a diff. disk, but set
the network adaptor as "Not
Connected." That way, I can get something quick
set up w/o having to worry too much about security.
I've been using both standard virtual disks and
differencing ones for quite some time now, and found
that differencing disks tend to end up using more disk
space. There seems to be a fundemental difference
between the two types of disks:
When you write a specific block to a standard virtual
disk for the first time, it is being allocated
(just-in-time), and then reused each time new data is
written to it.
The diff disk is basically a log of all write
operations. So if a block is being re-written, it
consumes more space with each write.
So diff disks are great for undo disks, where you want
to change stuff and then commit or rollback, causing the
diff log to be cleared. But they are not so great for
continuous operation.
For example, I was using both a diff disk and a standard
virtual one for about 5 months, using both for Windows
2003 + SQL + doing some development on Visual Studio.
They both spawned from the same root 5GB virtual disk.
The diff disk reached 13.6GB when I quit using it. The
standard disk used only 6.3GB.