On Wed, 22 Aug 2007, Dmitry Koterov wrote:
I have written a small perl script to check how slow is fsync for Smart Array E200i controller. Theoretically, because of write cache, fsync MUST cost nothing, but in practice it is not true
That theory is fundamentally flawed; you don't know what else is in the operating system write cache in front of what you're trying to fsync, and you also don't know exactly what's in the controller's cache when you start. For all you know, the controller might be filled with cached reads and refuse to kick all of them out. This is a complicated area where tests are much more useful than trying to predict the behavior.
You haven't mentioned any details yet about the operating system you're running on; Solaris? Guessing from the device name. There have been some comments passing by lately about the write caching behavior not being turned on by default in that operating system.
-- * Greg Smith gsmith@xxxxxxxxxxxxx http://www.gregsmith.com Baltimore, MD ---------------------------(end of broadcast)--------------------------- TIP 4: Have you searched our list archives? http://archives.postgresql.org/
