While EXT4 may or may not work with CloneZilla / PartedMagic (I have not tested lately, but my last attempt failed miserably), fsarchiver is a very handy little tool for creating an image of this version of the standard Linux filesystem.
Making an image of a partition/filesystem is relatively simple:
fsacrhiver [-v] savefs destination source
For example, to backup the /dev/md0 filesystem to /backup/md0-backup.fs, run
fsarchiver -v -z 5 -j 2 savefs /backup/cnt/md0.fs /dev/md0
v = verbose
z = 0…9 (compression level, 0 being max)
j = number of compression threads (equal to the number of CPU cores available)