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

Munehiro Ikeda m-ikeda at ds.jp.nec.com
Mon Aug 31 09:40:29 PDT 2009

Hello Dong-Jae,

Dong-Jae Kang wrote, on 08/31/2009 03:16 AM:
> Hi Munehiro Ikeda
> Thanks for your attention.
> and sorry for late reply.

No problem.

> 2009/8/29 Munehiro Ikeda <m-ikeda at ds.jp.nec.com
> <mailto: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.

Alright, I see.  Completely no fluctuation in direct write is interesting.
Thank you for the explanation.


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

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