On Mon, May 2, 2011 at 7:44 AM, Greg Stark <gsst...@mit.edu> wrote: > On Sun, May 1, 2011 at 9:31 PM, Simon Riggs <si...@2ndquadrant.com> wrote: >> I don't think the performance of replication is at issue. This is >> about resource control. >> > > The unspoken question here is why would replication be affected by i/o > load anyways? It's reading data file buffers that have only recently > been written and should be in cache. I wonder if this system has > chosen O_DIRECT or something like that for writing out wal?
It's not, that is a misunderstanding in the thread. It appears that the sheer volume of WAL being generated slows down replication. I would guess it's the same effect as noticing a slow down on web traffic when somebody is watching streaming video. The requested solution is the same as the network case: rate limit the task using too much resource, if the user requests that. I can't see the objection to replacing something inadvertently removed in 9.0, especially since it is a 1 line patch and is accompanied by copious technical evidence. Sure, we can do an even better job in a later release. -- Simon Riggs http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
