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Old 12-21-2010, 09:01 PM
Antonello Piemonte
 
Default I/O size distribution?

Hello

I have read that under Solaris one can use DTrace to get I/O request
size distribution on a global scale (also on a per process/pid basis).
See for example

http://prefetch.net/articles/observeiodtk.html

Can anyone*recommend*an alternative to get similar information under
CentOS? I looked into dtrace for linux but it seems still work in
progress, even putting aside CDDL issues ...

http://www.crisp.demon.co.uk/tools.html

Thanks!
Antonello
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Old 12-21-2010, 09:49 PM
Keith Roberts
 
Default I/O size distribution?

On Tue, 21 Dec 2010, Antonello Piemonte wrote:


To: centos@centos.org
From: Antonello Piemonte <apiemont@googlemail.com>
Subject: [CentOS] I/O size distribution?

Hello

I have read that under Solaris one can use DTrace to get I/O request
size distribution on a global scale (also on a per process/pid basis).
See for example

http://prefetch.net/articles/observeiodtk.html

Can anyone*recommend*an alternative to get similar information under
CentOS? I looked into dtrace for linux but it seems still work in
progress, even putting aside CDDL issues ...


This might do it. It's in the updates repo.

Name : systemtap
Arch : i386
Version : 1.1
Release : 3.el5_5.3
Size : 6.3 M
Repo : installed
Summary : Instrumentation System
URL : http://sourceware.org/systemtap/
License : GPLv2+
Description: SystemTap is an instrumentation system for
systems running Linux 2.6.
: Developers can write instrumentation to collect
data on the operation

: of the system.

Kind Regards,

Keith Roberts

--
In theory, theory and practice are the same;
in practice they are not.

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Old 12-21-2010, 10:06 PM
JohnS
 
Default I/O size distribution?

On Tue, 2010-12-21 at 23:01 +0100, Antonello Piemonte wrote:
> Hello
>
IOTOP from here [1]. From a very quick glance of the Specfile it should
build with no problems under EL5.

John

[1] http://guichaz.free.fr/iotop/

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Old 12-21-2010, 11:54 PM
Jeff Layton
 
Default I/O size distribution?

On 12/21/2010 05:01 PM, Antonello Piemonte wrote:
> Hello
>
> I have read that under Solaris one can use DTrace to get I/O request
> size distribution on a global scale (also on a per process/pid basis).
> See for example
>
> http://prefetch.net/articles/observeiodtk.html
>
> Can anyone recommend an alternative to get similar information under
> CentOS? I looked into dtrace for linux but it seems still work in
> progress, even putting aside CDDL issues ...
>

If you want to look at the specific run of an application and
not the system as a whole or on a continual basis, then you
can use strace.

However, this can produce a great deal of data. So I wrote a
simple tool to scan through the strace output file and produce
some statistics. You can download it at:

http://clusterbuffer.wetpaint.com/page/Strace+Analyzer

The version that is on the website is currently a bit dated with
a few bugs in it. I should be posting the latest version in the
next couple of weeks.

Thanks!

Jeff

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Old 12-22-2010, 05:32 AM
Rajagopal Swaminathan
 
Default I/O size distribution?

Greetings,

On Tue, Dec 21, 2010 at 10:01 PM, Antonello Piemonte
<apiemont@googlemail.com> wrote:
> Hello
>
> I have read that under Solaris one can use DTrace to get I/O request

I have heard that Dag or rf has it?

No guarantees!

Regards

Rajagopal
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Old 12-22-2010, 05:52 AM
"Geoff Galitz"
 
Default I/O size distribution?

......
>
> I have read that under Solaris one can use DTrace to get I/O request
> size distribution on a global scale (also on a per process/pid basis).
> See for example
>
> http://prefetch.net/articles/observeiodtk.html
>
> Can anyone recommend an alternative to get similar information under
> CentOS? I looked into dtrace for linux but it seems still work in
> progress, even putting aside CDDL issues ...
>
> http://www.crisp.demon.co.uk/tools.html
>

You can try SystemTap: http://sourceware.org/systemtap/

It seems to be roughly analagous to dtrace and is aimed squarly at the linux
kernel.



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Old 12-22-2010, 08:08 PM
Antonello Piemonte
 
Default I/O size distribution?

Thanks for all the suggestions.

I had a look at systemtap but I have the feeling that in it's current
state it is aimed more at kernel developers rather than average admins
like me :-)

Still, I'll keep an eye on it also give the fact that there seem to be
now new documentation being written about it

http://docs.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/5/pdf/SystemTap_Beginners_Guide/SystemTap_Beginners_Guide.pdf

On the other end, I have discovered blktrace and related tools, and
this seems more palatable to me (subjective, I know ...). This example
in particular seems to work for me

# blktrace /dev/sda -a issue -a complete -w 60 -o - | blkiomon -I 4 -h -

thought to share in case anyone finds it useful.

cheers
A.
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Old 12-22-2010, 09:05 PM
Keith Roberts
 
Default I/O size distribution?

On Wed, 22 Dec 2010, Antonello Piemonte wrote:

> To: CentOS mailing list <centos@centos.org>
> From: Antonello Piemonte <apiemont@googlemail.com>
> Subject: Re: [CentOS] I/O size distribution?
>
> Thanks for all the suggestions.
>
> I had a look at systemtap but I have the feeling that in it's current
> state it is aimed more at kernel developers rather than average admins
> like me :-)
>
> Still, I'll keep an eye on it also give the fact that there seem to be
> now new documentation being written about it
>
> http://docs.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/5/pdf/SystemTap_Beginners_Guide/SystemTap_Beginners_Guide.pdf
>
> On the other end, I have discovered blktrace and related tools, and
> this seems more palatable to me (subjective, I know ...). This example
> in particular seems to work for me
>
> # blktrace /dev/sda -a issue -a complete -w 60 -o - | blkiomon -I 4 -h -
>
> thought to share in case anyone finds it useful.

Can I use this to monitor which files are being written to
disk?

Keith

--
In theory, theory and practice are the same;
in practice they are not.

This email was sent from my laptop with Centos 5.5
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Old 12-23-2010, 06:19 AM
 
Default I/O size distribution?

Antonello Piemonte wrote:
> Hello
>
> I have read that under Solaris one can use DTrace to get I/O request
> size distribution on a global scale (also on a per process/pid basis).
> See for example
>
> http://prefetch.net/articles/observeiodtk.html
>
> Can anyone*recommend*an alternative to get similar information under
> CentOS? I looked into dtrace for linux but it seems still work in
> progress, even putting aside CDDL issues ...
>
> http://www.crisp.demon.co.uk/tools.html

Maybe the average request size from
iostat -x
could supply part of the /global/ piece?
--
Charles Polisher

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Old 12-23-2010, 07:06 AM
Antonello Piemonte
 
Default I/O size distribution?

@ Charles Polisher

yes, seems that avgrq-sz does provide the info I needed, thanks for
pointing that out!

@ Keith

I am not sure if blktrace can monitor which files being written to
disk or if it is the best tool for that.
But you could check out the inotify-tools (iwatch and related) which
go on that directions.
An example usage is here

http://openquery.com/blog/tool-day-inotify

or iwatch

http://iwatch.sourceforge.net/index.html

cheers
Antonello
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