linux-kernel - Re: Abysmal disk performance, how to debug?

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Date:	Sun, 21 Jan 2007 05:17:18 +0530
From:	"Sunil Naidu" <akula2.shark@...il.com>
To:	"Tim Schmielau" <tim@...sik3.uni-rostock.de>
Cc:	"Ismail Dönm" <ismail@...dus.org.tr>,
	"Willy Tarreau" <w@....eu>, lkml <linux-kernel@...r.kernel.org>
Subject: Re: Abysmal disk performance, how to debug?

On 1/21/07, Tim Schmielau <tim@...sik3.uni-rostock.de> wrote:
> Yes. You have a faster Disk that writes about 45 MB/s. But I am not sure I
> understand what you want to know?

I got these results with a customized 2.6.20-rc5.

[sukhoi@...hoon kernel]$ uname -a
Linux Typhoon 2.6.20-rc5-Topol-M #1 SMP Sun Jan 21 04:35:28 IST 2007
i686 i686 i386 GNU/Linux


> > [sukhoi@...hoon ~]$ time dd if=/dev/zero of=/tmp/1GB bs=1M count=1024; time
> > sync
> > 1024+0 records in
> > 1024+0 records out
> > 1073741824 bytes (1.1 GB) copied, 19.5007 seconds, 55.1 MB/s
> >
> > real    0m20.439s
> > user    0m0.004s
> > sys     0m4.535s
> >
> > real    0m4.625s
> > user    0m0.000s
> > sys     0m0.125s

[sukhoi@...hoon kernel]$ time dd if=/dev/zero of=/tmp/1GB bs=1M count=1024; time
1024+0 records in
1024+0 records out
1073741824 bytes (1.1 GB) copied, 22.7749 seconds, 47.1 MB/s

real    0m24.541s
user    0m0.005s
sys     0m3.899s

real    0m0.000s
user    0m0.000s
sys     0m0.000s

> >
> > [sukhoi@...hoon ~]$ time dd if=/dev/zero of=/tmp/1GB bs=1M count=1024 | sync
> > 1024+0 records in
> > 1024+0 records out
> > 1073741824 bytes (1.1 GB) copied, 20.8707 seconds, 51.4 MB/s
> >
> > real    0m22.449s
> > user    0m0.002s
> > sys     0m4.922s

[sukhoi@...hoon kernel]$ time dd if=/dev/zero of=/tmp/1GB bs=1M
count=1024 | sync
1024+0 records in
1024+0 records out
1073741824 bytes (1.1 GB) copied, 19.8685 seconds, 54.0 MB/s

real    0m21.373s
user    0m0.003s
sys     0m3.859s

> > Linux used here is not 2.6.20-rc5, but it's a FC6 2.6.19 binary. Shall
> > post the results with 2.6.20-rc5.
> >
> > BTW, does the results vary with a customized kernel (configured w.r.t
> > Processor & Hardware) than a generic kernel like FC6?
>
> I'd guess the kernel won't make much of a difference as the time is
> mostly determined by RAM and disk speeds.

There is some deviation in the results between these 2 kernels. Is
this acceptable?

> > Are there any other such test cases?
>
> Well, what do you want to find out? Anyways, I am in no way expert in the
> field of benchmarking.

I would be trying to benchmark the results on my machines in this
fashion (overclocking experiment):-

Disk Types                                       Machine
                            RAM

SATA 1.5 GBPS  - 160 GB           P4-HT-3.0 GHz
   2x1GB Corsair
SATA 3.0 GBPS  -  320 GB          P4-HT-3.0 GHz
   2x1GB Corsair

SATA 1.5 GBPS  -  160 GB           P4-HT-3.0 GHz
   2x1GB OCZ
SATA 3.0 GBPS  -   320 GB           P4-HT-3.0 GHz
    2x1GB OCZ

SATA 1.5 GBPS  -  160 GB              P4-HT-3.0 GHz
    2x1GB Supertalent
SATA 3.0 GBPS  -   320 GB             P4-HT-3.0 GHz
    2x1GB Supertalent

SATA 1.5 GBPS  -  160 GB             P4-HT-3.0 GHz
    2x1GB Hynix
SATA 3.0 GBPS  -   320 GB            P4-HT-3.0 GHz
     2x1GB Hynix

Boards here would be used are Intel based 915, 965, and 975.

Would be happy to know more test cases - for RAM/Disk/Processor Frequency

And, I don't work for any magazine, writing a review ;-)

>
> Tim

Thanks,

~Akula2
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