Re: SATA Harddisk speed drop of 100 MB/s

From: Henrique de Moraes Holschuh <hmh@hmh.eng.br>
To: Carlo Wood <carlo@alinoe.com>,
	Arjan van de Ven <arjan@infradead.org>,
	Jeff Garzik <jeff@garzik.org>,
	linux-kernel@vger.kernel.org
Subject: Re: SATA Harddisk speed drop of 100 MB/s
Date: Fri, 22 Jun 2007 22:31:32 -0300	[thread overview]
Message-ID: <20070623013132.GA1702@khazad-dum.debian.net> (raw)
In-Reply-To: <20070622212758.GA6970@alinoe.com>

Hi Carlo!

On Fri, 22 Jun 2007, Carlo Wood wrote:

> On Fri, Jun 22, 2007 at 06:17:46PM -0300, Henrique de Moraes Holschuh wrote:
> > On Fri, 22 Jun 2007, Carlo Wood wrote:
> > > So far I found out that it's RAID only.
> > 
> > If you change the IO schedulers, does it help?
> 
> How do I do that?

for i in /sys/block/sd*/queue/scheduler ; do echo -n "scheduler for $i was:" ; cat $i ; echo anticipatory > $i ; done

Should show you the scheduler for all libata/scsi discs, and switch to
anticipatory.  It probably works for hd* as well, but I don't have any
around to test.

I had ridiculous md raid performance (on resync) using cfq at least once.
Unfortunately I never bothered trying to track it down, and I didn't check
the throughput after the resync was done either. Also, I don't recall the
kernel version, but it was either 2.6.18 or 2.6.20.

Since it is a very simple test...

-- 
  "One disk to rule them all, One disk to find them. One disk to bring
  them all and in the darkness grind them. In the Land of Redmond
  where the shadows lie." -- The Silicon Valley Tarot
  Henrique Holschuh