On Tue, 6 Jan 2015 08:26:22 -0500 Robert Haas <robertmh...@gmail.com> wrote:
> Three, scan the WAL generated since the incremental backup and summarize it > into a list of blocks that need to be backed up. This can be done from the archive side. I was talking about some months ago now: http://www.postgresql.org/message-id/51c4dd20.3000...@free.fr One of the traps I could think of it that it requires "full_page_write=on" so we can forge each block correctly. So collar is that we need to start a diff backup right after a checkpoints then. And even without "full_page_write=on", maybe we could add a function, say "pg_start_backupdiff()", which would force to log full pages right after it only, the same way "full_page_write" does after a checkpoint. Diff backups would be possible from each LSN where we pg_start_backupdiff'ed till whenever. Building this backup by merging versions of blocks from WAL is on big step. But then, there is a file format to define, how to restore it and to decide what tools/functions/GUCs to expose to admins. After discussing with Magnus, he adviced me to wait for a diff backup file format to emerge from online tools, like discussed here (by the time, that was Michael's proposal based on pg_basebackup that was discussed). But I wonder how easier it would be to do this the opposite way? If this idea of building diff backup offline from archives is possible, wouldn't it remove a lot of trouble you are discussing here? Regards, -- Jehan-Guillaume de Rorthais Dalibo http://www.dalibo.com -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
