| From: | Greg Smith <gsmith(at)gregsmith(dot)com> |
|---|---|
| To: | Mark Mielke <mark(at)mark(dot)mielke(dot)cc> |
| Cc: | Andrej Ricnik-Bay <andrej(dot)groups(at)gmail(dot)com>, Scott Marlowe <scott(dot)marlowe(at)gmail(dot)com>, "pgsql-performance(at)postgresql(dot)org" <pgsql-performance(at)postgresql(dot)org> |
| Subject: | Re: file system and raid performance |
| Date: | 2008-08-08 22:30:07 |
| Message-ID: | Pine.GSO.4.64.0808081809430.21924@westnet.com |
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| Thread: | |
| Lists: | pgsql-performance |
On Thu, 7 Aug 2008, Mark Mielke wrote:
> Now, modern Linux distributions default to "relatime"
Right, but Mark's HP test system is running Gentoo.
(ducks)
According to http://brainstorm.ubuntu.com/idea/2369/ relatime is the
default for Fedora 8, Mandriva 2008, Pardus, and Ubuntu 8.04.
Anyway, there aren't many actual files involved in this test, and I
suspect the atime writes are just being cached until forced out to disk
only periodically. You need to run something that accesses more files
and/or regularly forces sync to disk periodically to get a more
database-like situation where the atime writes degrade performance. Note
how Joshua Drake's ext2 vs. ext3 comparison, which does show a large
difference here, was run with the iozone's -e parameter that flushes the
writes with fsync. I don't see anything like that in the DL380 G5 fio
tests.
--
* Greg Smith gsmith(at)gregsmith(dot)com http://www.gregsmith.com Baltimore, MD
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