> What I don't understand is: aren't zfs snapshots writable, like in btrfs?
ZFS snapshots, following the historic meaning of "snapshot", are read-only. ZFS supports cloning of a read-only snapshot to a writable volume/file system.
Btrfs is actually the one 'corrupting' the already-accepted nomenclature of snapshots meaning a read-only copy of the data.
I would assume the etymology of the file system concept of a "snapshot" derives from photography, where something is frozen at a particular moment of time:
> In computer systems, a snapshot is the state of a system at a particular point in time. The term was coined as an analogy to that in photography. […] To avoid downtime, high-availability systems may instead perform the backup on a snapshot—a read-only copy of the data set frozen at a point in time—and allow applications to continue writing to their data. Most snapshot implementations are efficient and can create snapshots in O(1).
ZFS snapshots, following the historic meaning of "snapshot", are read-only. ZFS supports cloning of a read-only snapshot to a writable volume/file system.
* https://openzfs.github.io/openzfs-docs/man/8/zfs-clone.8.htm...
Btrfs is actually the one 'corrupting' the already-accepted nomenclature of snapshots meaning a read-only copy of the data.
I would assume the etymology of the file system concept of a "snapshot" derives from photography, where something is frozen at a particular moment of time:
> In computer systems, a snapshot is the state of a system at a particular point in time. The term was coined as an analogy to that in photography. […] To avoid downtime, high-availability systems may instead perform the backup on a snapshot—a read-only copy of the data set frozen at a point in time—and allow applications to continue writing to their data. Most snapshot implementations are efficient and can create snapshots in O(1).
* https://en.wikipedia.org/wiki/Snapshot_(computer_storage)
* https://en.wikipedia.org/wiki/Snapshot_(photography)