On Thu, Jul 31, 2014 at 5:26 AM, desmodemone <desmodemone@gmail.com> wrote:
> b) yes the backends need to update the map, but it's in memory, and as I
> show, could be very small if we you chunk of blocks.If we not compress the
> map, I not think could be a bottleneck.
If it's in memory, it's not crash-safe. For something aimed at
backups, I think crash safety is a requirement. So it's at least one
extra I/O per commit, maybe less if many can be coalesced at
checkpoints, but I wouldn't count on it too much, because worst cases
are easy to come by (sparse enough updates).
I think this could be pegged on WAL replay / checkpoint stuff alone,
so it would be very asynchronous, but not free.
