On Tue, Aug 5, 2014 at 9:04 PM, Simon Riggs <si...@2ndquadrant.com> wrote: > On 5 August 2014 22:38, Claudio Freire <klaussfre...@gmail.com> wrote: > >>> * When we take an incremental backup we need the WAL from the backup >>> start LSN through to the backup stop LSN. We do not need the WAL >>> between the last backup stop LSN and the new incremental start LSN. >>> That is a huge amount of WAL in many cases and we'd like to avoid >>> that, I would imagine. (So the space savings aren't just the delta >>> from the main data files, we should also look at WAL savings). >> >> Yes, probably something along the lines of removing redundant FPW and >> stuff like that. > > Not what I mean at all, sorry for confusing. > > Each backup has a start LSN and a stop LSN. You need all the WAL > between those two points (-X option) > > But if you have an incremental backup (b2), it depends upon an earlier > backup (b1). > > You don't need the WAL between b1.stop_lsn and b2.start_lsn. > > In typical cases, start to stop will be a few hours or less, whereas > we'd be doing backups at most daily. Which would mean we'd only need > to store at most 10% of the WAL files because we don't need WAL > between backups.
I was assuming you wouldn't store that WAL. You might not even have it. -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers