----- Mensagem original ----- | Andrà Volpato wrote: | > | | > | If it is being spent in the bitmap index scan, try setting | > | effective_io_concurrency to 0 for Linux, and see what effect that | > | has. | > | > I disabled effective_io_concurrency at AIX but it made no changes on | > bitmap index times. | > | | Brad's point is that it probably doesn't do anything at all on AIX, | and is already disabled accordingly. But on Linux, it is doing something, | and that might be contributing to why it's executing so much better on | that platform. If you disable that parameter on your Debian box, that | should give you an idea whether that particular speed-up is a major | component to the difference you're seeing or not. Cant do it right now, but will do it ASAP and post here. | Also, if the system check was done by the "vendor team" team, don't | trust them at all. It doesn't sound like a disk problem is involved in | your case yet, but be sure to do your own basic disk benchmarking too | rather than believing what you're sold. There's a quick intro to that | at | http://www.westnet.com/~gsmith/content/postgresql/pg-disktesting.htm | and a much longer treatment of the subject in my book if you want a | lot | more details. I don't have any AIX-specific tuning advice in there | though.| IÂm gonna read your sugestion, thanks. We tested the disks also, and we did a lot of tuning to get acceptable transfer rates at AIX. Yesterday I tried your "stream-scaling" and get around 7000MB/s (single thread) and 10000MB/s (eight threads) at AIX, and a little less than that at Debian, since its a virtual box. I found that even my notebook is close to that transfer rates, and both boxes are limited by DDR2 speeds. | -- | Greg Smith 2ndQuadrant US greg@xxxxxxxxxxxxxxx Baltimore, MD | PostgreSQL Training, Services and Support www.2ndQuadrant.us | "PostgreSQL 9.0 High Performance": http://www.2ndQuadrant.com/books []Âs, Andrà Volpato -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
