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From: Michael Tokarev <mjt@tls.msk.ru>
To: Justin Piszcz <jpiszcz@lucidpixels.com>
Cc: linux-kernel@vger.kernel.org, linux-raid@vger.kernel.org,
	xfs@oss.sgi.com
Subject: Re: Linux Software RAID 5 Performance Optimizations: 2.6.19.1: (211MB/s read & 195MB/s write)
Date: Fri, 12 Jan 2007 17:01:24 +0300	[thread overview]
Message-ID: <45A794B4.5020608@tls.msk.ru> (raw)
In-Reply-To: <Pine.LNX.4.64.0701111832080.3673@p34.internal.lan>

Justin Piszcz wrote:
> Using 4 raptor 150s:
> 
> Without the tweaks, I get 111MB/s write and 87MB/s read.
> With the tweaks, 195MB/s write and 211MB/s read.
> 
> Using kernel 2.6.19.1.
> 
> Without the tweaks and with the tweaks:
> 
> # Stripe tests:
> echo 8192 > /sys/block/md3/md/stripe_cache_size
> 
> # DD TESTS [WRITE]
> 
> DEFAULT: (512K)
> $ dd if=/dev/zero of=10gb.no.optimizations.out bs=1M count=10240
> 10240+0 records in
> 10240+0 records out
> 10737418240 bytes (11 GB) copied, 96.6988 seconds, 111 MB/s
[]
> 8192K READ AHEAD
> $ dd if=10gb.16384k.stripe.out of=/dev/null bs=1M
> 10240+0 records in
> 10240+0 records out
> 10737418240 bytes (11 GB) copied, 64.9454 seconds, 165 MB/s

What exactly are you measuring?  Linear read/write, like copying one
device to another (or to /dev/null), in large chunks?

I don't think it's an interesting test.  Hint: how many times a day
you plan to perform such a copy?

(By the way, for a copy of one block device to another, try using
O_DIRECT, with two dd processes doing the copy - one reading, and
another writing - this way, you'll get best results without huge
affect on other things running on the system.  Like this:

 dd if=/dev/onedev bs=1M iflag=direct |
 dd of=/dev/twodev bs=1M oflag=direct
)

/mjt

  reply	other threads:[~2007-01-12 14:01 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-01-11 23:38 Justin Piszcz
2007-01-12 14:01 ` Michael Tokarev [this message]
2007-01-12 14:38   ` Justin Piszcz
2007-01-12 17:37     ` Justin Piszcz
2007-01-12 19:49       ` Al Boldi
2007-01-12 19:56         ` Justin Piszcz
2007-01-12 20:15           ` Justin Piszcz
2007-01-12 20:41             ` Bill Davidsen
2007-01-12 21:00             ` Al Boldi
2007-01-12 21:40               ` Justin Piszcz
2007-01-13  6:11                 ` Al Boldi
2007-01-13  9:40                   ` Justin Piszcz

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