Re: file system and raid 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@gregsmith.com http://www.gregsmith.com Baltimore, MD