ZFS is an advanced file system with integrated multi-device volume management. It was originally designed and implemented by Sun Microsystems for their Unix operating system Solaris. The copyright for the original codebase is now owned by Oracle and has since been closed up and made proprietary software. Prior to Oracle's acquisition of Sun, ZFS was made open source under the CDDL as part of OpenSolaris, that code was forked and it gave rise to OpenZFS which is used by many Linux and BSD users.

https://en.wikipedia.org/wiki/ZFS

https://openzfs.org

Here are a couple of introductions.

https://news.ycombinator.com/item?id=25157491

https://www.linuxjournal.com/content/zfs-linux

It's like someone glued together LVM and RAID but on file level instead of block level.

So you can make some fancy things like (relatively) cost-free snapshots, and some extra data safety with per-file checksumming. It also uses WAL (similarly to databases) which allows (similiar to databases) replication to remote system.

Got it, that makes sense! Not OP but a followup - what does "replication" mean in this context? Is it mirroring your ZFS volumes in another device?

Pretty much, although it's one-directional transfer of a volume or snapshot of one, not bi-directional one