On Tue, Jan 14, 2014 at 2:16 PM, Michael Paquier <michael.paqu...@gmail.com>wrote:
> On Tue, Jan 14, 2014 at 10:01 PM, Heikki Linnakangas > <hlinnakan...@vmware.com> wrote: > >> - Addition of an option called INCREMENTAL to send an incremental > >> backup to the client. This option uses as input an LSN, and sends back > >> to client relation pages (in the shape of reduced relation files) that > >> are newer than the LSN specified by looking at pd_lsn of > >> PageHeaderData. In this case the LSN needs to be determined by client > >> based on the latest full backup taken. This option is particularly > >> interesting to reduce the amount of data taken between two backups, > >> even if it increases the restore time as client needs to reconstitute > >> a base backup depending on the recovery target and the pages modified. > >> Client would be in charge of rebuilding pages from incremental backup > >> by scanning all the blocks that need to be updated based on the full > >> backup as the LSN from which incremental backup is taken is known. But > >> this is not really something the server cares about... Such things are > >> actually done by pg_rman as well. > > > > > > How does the server find all the pages with LSN > the threshold? If it > needs > > to scan the whole database, it's not all that useful. I guess it would be > > better than nothing, but I think you might as well just use rsync. > Yes, it would be necessary to scan the whole database as the LSN to be > checked is kept in PageHeaderData :). Perhaps it is not that > performant, but my initial thought was that perhaps the amount of data > necessary to maintain incremental backups could balance with the > amount of WAL necessary to keep and limit the whole amount on disk. > It wouldn't be worse performance wise than a full backup. That one also has to read all the blocks after all... You're decreasing network traffic and client storage, with the same I/O on the server side. Seems worthwhile. -- Magnus Hagander Me: http://www.hagander.net/ Work: http://www.redpill-linpro.com/
