rsync backup size

[Smoot Carl-Mitchell]

On Wed, 2009-02-18 at 00:32 -0700, Robert Holtzman wrote:
> I run rsync with the command:
> 
> sudo rsync -vaHz --exclude '/proc' --exclude '/sys' --exclude '/media' / 
> /media/disk
> 

> 2. Running "du -ach /media/disk" showed ~8 Gb (the backup is the only 
> thing on the disk). Running "du -ach /" (with the usb disk removed) 
> showed ~6 Gb. Why is the backup larger than the system, especially 
> since I invoked the z option and was careful to exclude /media?

You may have some "sparse" (e.g. files with some blocks which are all
zero bytes) files on the source filesystem.  You might try the -S flag
which will handle sparse files more efficiently.  This should save space
unless the destination filesystem does not support sparse files.
-- 
Smoot Carl-Mitchell
Computer Systems and
Network Consultant
smoot at tic.com
+1 480 922 7313
cell: +1 602 421 9005