ZFS is a game changer for quickly and reliably backing up large multi-terabyte PostgreSQL databases as well. In case anyone is interested, here is our experience with PostgreSQL on ZFS, complete with a short backup script: https://lackofimagination.org/2022/04/our-experience-with-po...

Came here to say this. Can you list your example commands for snapshotting, zfs send, restoring single files or entire snapshots, etc.? (Have you tested it out?) I am actually in the position of doing this (I use zfs on root as of recently and I have a TrueNAS) but am stuck at the bootstrapping problem (I haven't taken a single snapshot yet; presumably the first one is the only big one? and then how do I send incremental snapshots? and then how do I restore these to, say, a new machine? do I remotely mount a snapshot somehow, or zfs recv, or? Do you set up systemd/cron jobs for this?) Also, having auto-snapshotted on Ubuntu in the past, eventually things slowed to a crawl every time I did an apt update... Is this avoidable?

Yes, the first snapshot is the big one, the rest are incremental. Restoring a snapshot is just one line really. Something like ;)

sudo zfs send -cRi db/data@2022-12-08T00-00 db/data@2022-12-09T00-00 | ssh me@backup-server "sudo zfs receive -vF db/data"

Zfs send/receive is nice but it does lack the toolchain to easily extract individual files from a backup. It's more of a disaster recovery thing in terms of backup.

You can actually extract individual files from a snapshot by using the hidden .zfs directory like: /mnt-point/.zfs/snapshot/snapshot-name

Another alternative is to create a clone from a snapshot, which also makes the data writable.

A snapshot yes but not a zfs send stream which is a single file.