Messages in this thread | | | From | Adam Radford <> | Subject | RE: File system performance, hardware performance, ext3, 3ware RA ID1, etc. | Date | Fri, 13 Feb 2004 15:07:22 -0800 |
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Perhaps you are issuing non purely sequential IO. The card firmware does some reodering, but at some point it will cause performance degradation. Can you try kernel 2.6 w/xfs?
Also, in my experience, the 'raw io' interface doesn't issue any asynchronous IO. The card _definately_ needs asynchronous IO posted to it or you will not get good results because you won't get all the drives busy.
-Adam
-----Original Message----- From: Timothy Miller [mailto:miller@techsource.com] Sent: Friday, February 13, 2004 2:57 PM To: Daniel Blueman Cc: linux-kernel@vger.kernel.org Subject: Re: File system performance, hardware performance, ext3, 3ware RAID1, etc.
Daniel Blueman wrote: > Willy Tarreau <willy@w.ods.org> wrote in message > news:<1oEGw-2ex-1@gated-at.bofh.it>... > >>On Thu, Feb 12, 2004 at 06:32:31PM -0500, Timothy Miller wrote: >> >> >>>For writes, iozone found an upper bound of about 10megs/sec, which is >>>abysmal. Typically, I'd expect writes to be faster (on a single drive) >>>than reads, because once the write is sent, you can forget about it. >>>You don't have to wait around for something to come back, and that >>>latency for reads can hurt performance. The OS can also buffer writes >>>and reorder them in order to improve efficiency. >> >>It depends on the disk too. Lots of disks (specially IDE) are far slower >>on writes than they are on reads. > > > No. Have you verified this? If you 'dd' your swap partition from /dev/zero > on IDE, you'll see write performance closely matches read performance, for > drives old and new. >
And this sort of things is what I find with raw writes to the model of drive I'm using. However, it seems that there must be some issue with the 3ware 7000-2 which is killing performance, or the way the Linux kernel is dealing with this sorta-SCSI device.
The WD1200JB should get like 30-40 megs/sec, but when being accessed through the 3ware, I get 10-16 megs/sec.
What could the 3ware be doing?
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