Am 15.11.2022 um 15:27 schrieb rhkra...@gmail.com: > I'm not really clear on the concept of a snapshot (for backup) -- I've done a > little googling but haven't found an explanation that "satisfies" me.
I am familiar with snapshots on zfs. There might be different meanings in other contexts, idk ... zfs is s COW filesystem, meaning "copy-on-write". Whenever you write to an already existing block (piece of a file), a new block gets created (copied and modified) and on closing the write (or on sync), the (metadata-) pointer/directory entry changes to point to the new block. This algorithm primarily implements transactions on the filesystem to garantee, it has a consistent state at all times. but one side effect is, that the old filesystem state still hangs around. And a snapshot basically points to that outdated state of a filesystem and keeping a shapshot means to prevent the reuse of those blocks until the snapshot gets freed up again. Does that help your understanding?