On 08/02/2024 06:38, J. Roeleveld wrote:
ZFS doesn't have this "max amount of changes", but will happily fill up the
entire pool keeping all versions available.
But it was easier to add zpool monitoring for this on ZFS then it was to add
snapshot monitoring to LVM.
I wonder, how do you deal with snapshots getting "full" on your system?
As far as I'm, concerned, snapshots are read-only once they're created.
But there is a "grow the snapshot as required" option.
I don't understand it exactly, but what I think happens is when I create
the snapshot it allocates, let's say, 1GB. As I write to the master
copy, it fills up that 1GB with CoW blocks, and the original blocks are
handed over to the backup snapshot. And when that backup snapshot is
full of blocks that have been "overwritten" (or in reality replaced),
lvm just adds another 1GB or whatever I told it to.
So when I delete a snapshot, it just goes through those few blocks,
decrements their use count (if they've been used in multiple snapshots),
and if the use count goes to zero they're handed back to the "empty" pool.
All I have to do is make sure that the sum of my snapshots does not fill
the lv (logical volume). Which in my case is a raid-5.
Cheers,
Wol
