Use a forensic analysis software like GUYMAGER (open source, sourceforge.net). It has a nice UI which allows to quickly create a compressed disk image of an entire hard disk.
Use "Advanced forensic image (.aff)" This creates a single, compressed file (well, it also creates an .info file).
To modify the default compression rate 1 (fastest, but least compression). If you have a fast computer with lots of cores, you can change this by creating
AffCompression = 3
9 is the best but slowest compression.
3 gives a good compression with good performance.
Mounting isn't as simple as it seems. First of all, you need AFFLIB (Ubuntu:
aptitude install afflib-tools). Now you can get the raw disk image with
[affuse] <image> <mount-point>
But for some reason, mounting the raw image fails.
parted says the first partition starts with
mount -t ext4 -o loop,ro,offset=1048576 /mnt/backup.raw /mnt/backup
fails with the usual useless mount error:
mount: wrong fs type, bad option, bad superblock on /dev/loop0,
missing codepage or helper program, or other error
In some cases useful info is found in syslog - try
dmesg | tail or so
EXT4-fs (loop0): VFS: Can't find ext4 filesystem