You didn't mention what type of media you want to back up to if not DVD or
NTFS volumes. There are reasons behind why we require NTFS or DVD and there
are also differences in the way they are treated:
--If the target is an NTFS volume, you can do incrementals. The differences
are stored as shadow copies within the shadow copy storage area on the
volume. The Volume ShadowCopy Service (VSS) is at the heart of these
incrementals, and VSS requires NTFS.
--If the target is an NTFS volume, you cannot compress the .vhd. This has to
do with the way in which the VSS service works--basically on the incremental
backup, any compression would lead to huge differences between the current
vhd and the one on the shadow copy and we will be deleting old shadow copies
at much higher rate. So the backup algorithm is highly optimized to cause as
little as possible copy-on-write to be able to keep more backups on the
target disk. (See blurb below for additional details on copy-oon-write.)
--If the target is DVD, then we do compress the .vhd but you can't do
incrementals because of the NTFS requirement for VSS.
Of course, none of this is obvious from the tool itself, but I wanted to let
you know that there are technical reasons behind the requirements.
Additional copy-on-write info I mentioned earlier.
"Copy-on-write" is Volume ShadowCopy (VSS) terminology. Complete PC Backup
uses shadow copies to store the incremental changes to .vhd file. These
updates are stored in a hidden area on your hard disk. This area is
configurable and can only hold so many shadow copies. Once the area fills,
oldest shadow copies are purged. The more changes on the volume, the more
quickly those older shadow copies will be purged. From what the developer
explained, the act of compressing a .vhd causes it to change more from
version to version. We want to avoid having those older shadow copies
purged, so we don't compress the .vhd on hard disks.
You can find explanations of "copy-on-write" in the Technical Reference at
http://technet2.microsoft.com/Windo...b7d8-42c3-b6c9-59c145b7765f1033.mspx?mfr=true.
Some internet searching also turns up good hits.
Here's a link to our blog for more info on shadow copies:
http://blogs.technet.com/filecab/ar...used-for-restore-points-in-windows-vista.aspx.