Tom Lane wrote: > Bruce Momjian <[EMAIL PROTECTED]> writes: > > Well, I wrote the program to allow testing. I don't see a complex test > > as being that much better than simple one. We don't need accurate > > numbers. We just need to know if fsync or O_SYNC is faster. > > Faster than what? The thing everyone is trying to point out here is > that it depends on context, and we have little faith that this test > program creates a context similar to a live Postgres database.
Note, too, that the preferred method isn't likely to depend just on the operating system, it's likely to depend also on the filesystem type being used. Linux provides quite a few of them: ext2, ext3, jfs, xfs, and reiserfs, and that's just off the top of my head. I imagine the performance of the various syncing methods will vary significantly between them. It seems reasonable to me that decisions such as which sync method to use should initially be made at installation time: have the test program run on the target filesystem as part of the installation process, and build the initial postgresql.conf based on the results. You might even be able to do some additional testing such as measuring the difference between random block access and sequential access, and again feed the results into the postgresql.conf file. This is no substitute for experience with the platform, but I expect it's likely to get you closer to something optimal than doing nothing. The only question, of course, is whether or not it's worth going to the effort when it may or may not gain you a whole lot. Answering that is going to require some experimentation with such an automatic configuration system. -- Kevin Brown [EMAIL PROTECTED] ---------------------------(end of broadcast)--------------------------- TIP 7: don't forget to increase your free space map settings
