On Tue, Oct 30, 2012 at 02:16:57PM +0100, Albe Laurenz wrote: > ktm@xxxxxxxx wrote: > >>> If you do not have good random io performance log replay is nearly > >>> unbearable. > >>> > >>> also, what io scheduler are you using? if it is cfq change that to > >>> deadline or noop. > >>> that can make a huge difference. > >> > >> We use the noop scheduler. > >> As I said, an identical system performed well in load tests. > > > The load tests probably had the "important" data already cached. > Processing > > a WAL file would involve bringing all the data back into memory using > a > > random I/O pattern. > > The database is way too big (1 TB) to fit into cache. > > What are "all the data" that have to be brought back? > Surely only the database blocks that are modified by the WAL, > right? > > Yours, > Laurenz Albe > Right, it would only read the blocks that are modified. Regards, Ken -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
