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Re: H800 + md1200 Performance problem

From: Cesar Martin <cmartinp(at)gmail(dot)com>
To: Tomas Vondra <tv(at)fuzzy(dot)cz>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: H800 + md1200 Performance problem
Date: 2012-04-03 15:42:34
Message-ID: CAMAsR=637=zAtOSxGF=JH9apfOtU7FaUXR27+J2syzE_c-rdYw@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-performance
Yes, setting is the same in both machines.

The results of bonnie++ running without arguments are:

Version      1.96   ------Sequential Output------ --Sequential Input-
--Random-
                    -Per Chr- --Block-- -Rewrite- -Per Chr- --Block--
--Seeks--
Machine        Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP  /sec
%CP
cltbbdd01      126G    94  99 202873  99 208327  95  1639  91 819392  88
 2131 139
Latency             88144us     228ms     338ms     171ms     147ms
20325us
                    ------Sequential Create------ --------Random
Create--------
                    -Create-- --Read--- -Delete-- -Create-- --Read---
-Delete--
files:max:min        /sec %CP  /sec %CP  /sec %CP  /sec %CP  /sec %CP  /sec
%CP
cltbbdd01        16  8063  26 +++++ +++ 27361  96 31437  96 +++++ +++ +++++
+++
Latency              7850us    2290us    2310us     530us      11us
522us

With DD, one core of CPU put at 100% and results are  about 100-170 MBps,
that I thing is bad result for this HW:

dd if=/dev/zero of=/vol02/bonnie/DD bs=8M count=100
100+0 records in
100+0 records out
838860800 bytes (839 MB) copied, 8,1822 s, 103 MB/s

dd if=/dev/zero of=/vol02/bonnie/DD bs=8M count=1000 conv=fdatasync
1000+0 records in
1000+0 records out
8388608000 bytes (8,4 GB) copied, 50,8388 s, 165 MB/s

dd if=/dev/zero of=/vol02/bonnie/DD bs=1M count=1024 conv=fdatasync
1024+0 records in
1024+0 records out
1073741824 bytes (1,1 GB) copied, 7,39628 s, 145 MB/s

When monitor I/O activity with iostat, during dd, I have noticed that, if
the test takes 10 second, the disk have activity only during last 3 or 4
seconds and iostat report about 250-350MBps. Is it normal?

I set read ahead to different values, but the results don't differ
substantially...

Thanks!

El 3 de abril de 2012 15:21, Tomas Vondra <tv(at)fuzzy(dot)cz> escribió:

> On 3.4.2012 14:59, Cesar Martin wrote:
> > Hi Mike,
> > Thank you for your fast response.
> >
> > blockdev --getra /dev/sdc
> > 256
>
> That's way too low. Is this setting the same on both machines?
>
> Anyway, set it to 4096, 8192 or even 16384 and check the difference.
>
> BTW explain analyze is nice, but it's only half the info, especially
> when the issue is outside PostgreSQL (hw, OS, ...). Please, provide
> samples from iostat / vmstat or tools like that.
>
> Tomas
>
> --
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>



-- 
César Martín Pérez
cmartinp(at)gmail(dot)com

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