Yes, I tried all WAL sync methods, but there was no difference... However, there was a huge difference when I run the same tests under Solaris10 - 'fdatasync' option gave the best performance level. On the same time direct I/O did not make difference on Solaris 10 :)
So the main rule - there is no universal rule :) just adapt system options according your workload... Direct I/O will generally speed-up write operation due avoiding buffer flashing overhead as well concurrent writing (breaking POSIX limitation of single writer per given file on the same time). But on the same time it may slow-down your read operations, and you may need 64bit PG version to use big cache to still keep same performance level on SELECT queries. And again, there are other file systems like QFS (for ex.) which may give you the best of both worlds: direct write and buffered read on the same time! etc. etc. etc. :) Rgds, -Dimitri On 7/9/07, Jonah H. Harris <[EMAIL PROTECTED]> wrote:
On 7/9/07, Jim C. Nasby <[EMAIL PROTECTED]> wrote: > BTW, it might be worth trying the different wal_sync_methods. IIRC, > Jonah's seen some good results from open_datasync. On Linux, using ext3, reiser, or jfs, I've seen open_sync perform quite better than fsync/fdatasync in most of my tests. But, I haven't done significant testing with direct I/O lately. -- Jonah H. Harris, Software Architect | phone: 732.331.1324 EnterpriseDB Corporation | fax: 732.331.1301 33 Wood Ave S, 3rd Floor | [EMAIL PROTECTED] Iselin, New Jersey 08830 | http://www.enterprisedb.com/
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