[Test Result] I/O bandwidth Control by dm-ioband - partition-based environment

Dong-Jae Kang baramsori72 at gmail.com
Mon Aug 31 00:16:31 PDT 2009

Hi Munehiro Ikeda

Thanks for your attention.
and sorry for late reply.
2009/8/29 Munehiro Ikeda <m-ikeda at ds.jp.nec.com>

> Hello Dong-Jae,
> Dong-Jae Kang wrote, on 08/26/2009 09:46 PM:
> Hi Ryo
>> I attached new test result file(ioband-partition-based-evaluation.xls)in
>> this mail.
>> In this time, it is not virtualization environment.
>> I evaluated partition-based use cases before I do it in vitualization
>> environment.
>> because I think the two cases are smilar each other.
>> The detailed information about the evaluation can be referred in attached
>> file.
>> If you have any questions or comments after examine it,
>> please give me your opinion.
>> Thank you.
> Good work.
> Please let me ask silly questions.
> (1) About what "target" means
> I guess "device" means writing to device files directly
> (--filename=/dev/mapper/ioband1)
> and "directory" means mounting these device files and writing to some
> directory
> on the filesystem
> (--filename=/mnt/ioband1/test.dat, I'm assuming mount /dev/mapper/ioband1
> on
> /mnt/ioband1),
> am I wright?

Yes, you are right.
I also think the terms can leave misunderstanding. :)

> (2) Conditions  in RDF sheet
> Conditions in sheet "RDF" and "RBF" are same but results are slightly
> different.
> Should "Mode" in RDF sheet be "Direct"?

As the Report sheet in the file shows,
"D" in RDF means Direct I/O and "B" in RBF means Buffered I/O(delayed I/O).
I think the reason for difference in result, especially several fluctuation
in RBF, is
related with buffer cache  and pdflushd daemon.
So, generally, I/O bandwidth controll in direct I/O mode is more accurate
than that of buffered I/O mode.

> Regards,
> Muuhh
> --
> IKEDA, Munehiro
>  NEC Corporation of America
>    m-ikeda at ds.jp.nec.com

Best Regards,
Dong-Jae Kang

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