Hi Martin,
I don't know if you are done, here's my summary, I've just used DFSee to backup and restore disk images in the past months:
- you can use it outside of running OS/2 or DFSee USB/CDboot. I made backups over usb{2,3} to sata/pata cables in macOS ported/compiled DFSee, needed about 10-12 minutes for a 2GB partition. Trying the same with about ~500 data in a partition trough an old phisycal PC with PATA showed around 1.5 hours time = gave up for another time.
- as Neil wrote you can choose a compressed image version, for disk image its created a *.imz, and *.xmz file. On a 2GB partition, filled above 1GB gave me ~847MB of files. So it is filesystem parsed imaging, not 1to1 disk2image, whatever the image format itself.
- I did both the partition and whole disk image. The latter can give you the ease of mind in restoring, with some Mbytes overhead. Thinking about booting, LVM and DLAT information.
- you can extract any files from the image were available in the original disk. I've had interesting boot/HPFS/LVM problems during one of my MCP2 UPDCD test/project in VM. It became a routine, to use a DFSee CDboot image to clear the HPFS dirty flag, or check if the HPFS contents are available, and try to manipulate/recover/fix LVM/DLAT info.