sudo dd if=/dev/sde1 | bzip2 –best > $(date +%Y%m%d_%H%M%S)_sde1-backup.bz2

or only read the used space and store it:
e2image -Qap /dev/sde1 sde1.qcow2
bzip2 -z hde1.qcow2

Convert it to a raw image (unzip it first)
e2image -r hde1.qcow2 hde1.raw