On Fri, Oct 22, 2010 at 12:05 PM, Kevin Grittner <Kevin.Grittner@xxxxxxxxxxxx> wrote: > Rob Wultsch <wultsch@xxxxxxxxx> wrote: > >> I would think full_page_writes=off + double write buffer should be >> far superior, particularly given that the WAL is shipped over the >> network to slaves. > > For a reasonably brief description of InnoDB double write buffers, I > found this: > > http://www.mysqlperformanceblog.com/2006/08/04/innodb-double-write/ > > One big question before even considering this would by how to > determine whether a potentially torn page "is inconsistent". > Without a page CRC or some such mechanism, I don't see how this > technique is possible. > > Even if it's possible, it's far from clear to me that it would be an > improvement. The author estimates (apparently somewhat loosely) > that it's a 5% to 10% performance hit in InnoDB; I'm far from > certain that full_page_writes cost us that much. Does anyone have > benchmark numbers handy? > > -Kevin > Ignoring (briefly) the cost in terms of performance of the different system, not needing full_page_writes would make geographically dispersed replication possible for certain cases where it is not currently (or at least rather painful). -- Rob Wultsch wultsch@xxxxxxxxx -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
