[TriLUG] backup windows with dd

[Joseph Mack NA3T]

To backup windows partitions (all vfat), I defragment and 
then run nullfile (which fills the rest of the partition 
with nulls). I then dd the partition on a linux machine, 
check that I can mount and read it, do an md5sum, then gzip 
the dd file. (I save the mbr, in case I need to restore a 
crashed disk.)

When I do this on one linux machine, the file which is 
output from the dd is the same size as the partition (about 
30G), and mounts fine and can be read. All OK. The windows 
partition is on a regular 3.5" hard disk on a desktop 
machine,

On another linux machine (and backing up different windows 
machines, with 40G laptop harddrives, which dual boot 
win/linux, with 10G win partitions) the dd output file is a 
little less than 6G and is the exact same size for several 
windows laptops. I assume I've run into some disk geometry 
limit. The partitions I'm dd'ing have <6G of windows files. 
I thought the 6G dd file must be truncated and unreadable, 
but when I mount the 6G dd file, I see the expected 
partition size (10G) in the mount table, du shows the right 
numbers for the number of bytes used/freee and the files in 
the partition all look OK.

I've got a 6G dd file which mounts as a correctly readable 
10G partition. I guess I've got a valid copy of the windows 
partition. However I'm worried that if I need to restore 
that the wrong sized partition will be written.

Anyone know why the dd copy of size 6G is not the same size 
as the 10G partition?

Thanks Joe
-- 
Joseph Mack NA3T EME(B,D), FM05lw North Carolina
jmack (at) wm7d (dot) net - azimuthal equidistant map
generator at http://www.wm7d.net/azproj.shtml
Homepage http://www.austintek.com/ It's GNU/Linux!