"Kevin Grittner" <[EMAIL PROTECTED]> wrote: > We have not experience any increase in I/O, just a smoothing. Keep in > mind that the file system cache will collapse repeated writes to the > same location until things settle, and the controller's cache also has a > chance of doing so. If we just push dirty pages out to the OS as soon > as possible, and let the file system do its job, I think we're in better > shape than if we try to micro-manage it within our buffer pages.
Maybe we have two entirely different tuning approaches: 1. Retain dirty buffers in database, and keep OS buffers clean. 2. Keep database clean, and entrust OS to manage dirty buffers. I suggested the 1st one, and you did the 2nd. Bottle-neck in checkpoints vary in the approaches; write() will be worse in 1st, fsync() in 2nd. Distributed write() is easier than distributed fsync(), because we can use write() on a page basis, but fsync() only on a file basis. Also, database has own access-frequency information for its buffers, so I think 1st approach behaves better in handling re-dirty of buffers. Regards, --- ITAGAKI Takahiro NTT Open Source Software Center ---------------------------(end of broadcast)--------------------------- TIP 3: Have you checked our extensive FAQ? http://www.postgresql.org/docs/faq