How small are these devices? I think the other problem is that neither BTRFS nor zfs really are suitable for removable devices, and definitely not for ones smaller than probably 8Gb at the very least.

Unlike NTFS which is just a file system, both BTRFS and ZFS do volume management too, so it’s not just a single partition thing; they prefer to take over an entire volume and manage everything.

So while they’re the closest filesystem with NTFS-like transparent compression…..they don’t match exactly.

I also hazard to guess if the devices you’re using are too small to accept a BTRFS formatted volume, no amount of compression is going to be enough to fit what you need.

If you just want to play with a bunch of small old devices…..maybe play with LVM and small RAID arrays and configurations instead. You can the build a bigger volume out of a bunch of those disks together and then put a BTRFS or zfs volume on them. Can be fun to experiment and learn with anyway.

How small is your smallest device? BTRFS doesn't have a minimum size, but practically probably 50-100mb is just about doable before even just setting things up get complex. Having said that though, it's copy-on-write and has overhead as a result, so may not function well below 1gb.

ZFS meanwhile really won't work well below probably 8gb. It's also copy-on-write but with a lot more overhead due to how it works. It really works best on big drives and filesystems.

If your old storage is in the mb range, then really neither will help you achieve what you want.

BTRFS and ZFS do offer the same benefits as NTFS with regard to compression and speeding up some slower devices (due to lowering the actual read/writes needed to achieve the same result as the data is compressed into a smaller space and decompressed rapidly by the PC in memory), but NTFS can go be used on much smaller disk sizes due to how it works. BTRFS and ZFS are designed and optimised with other benefits in mind. And NTFS compression isn't well supported in Linux.

For ZFS check the instruction for your distribution here: https://openzfs.github.io/openzfs-docs/Getting%20Started/index.html

PM me if you need help with ZFS. I've gotten quite good at setting it up.