Date: Thu, 08 Oct 2009 19:22:42 +0900 (JST)
Message-Id: <20091008.192242.39182274.ryov@valinux.co.jp>
To: riel@redhat.com
Cc: vgoyal@redhat.com, nauman@google.com, m-ikeda@ds.jp.nec.com,
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Subject: Re: IO scheduler based IO controller V10
From: Ryo Tsuruta <ryov@valinux.co.jp>
In-Reply-To: <4ACCC4B7.4050805@redhat.com>
References: <20091006112201.GA27866@redhat.com>
	<20091007.233805.183040347.ryov@valinux.co.jp>
	<4ACCC4B7.4050805@redhat.com>
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Hi Rik,

Rik van Riel <riel@redhat.com> wrote:
> Ryo Tsuruta wrote:
> 
> > If once dm-ioband is integrated into the LVM tools and bandwidth can
> > be assigned per device by lvcreate, the use of dm-tools is no longer
> > required for users.
> 
> A lot of large data center users have a SAN, with volume management
> handled SAN-side and dedicated LUNs for different applications or
> groups of applications.
> 
> Because of alignment issues, they typically use filesystems directly
> on top of the LUNs, without partitions or LVM layers.  We cannot rely
> on LVM for these systems, because people prefer not to use that.

Thank you for your explanation. So I have a plan to reimplement
dm-ioband into the block layer to make dm-tools no longer required.
My opinion I wrote above assumes if dm-ioband is used for a logical
volume which consists of multiple physical devices. If dm-ioband is
integrated into the LVM tools, then the use of the dm-tools is not
required and the underlying physical devices can be automatically
deteced and configured to use dm-ioband.

Thanks,
Ryo Tsuruta

> Besides ... isn't the goal of the cgroups io bandwidth controller
> to control the IO used by PROCESSES?
>
> If we want to control processes, why would we want the configuration
> to be applied to any other kind of object in the system?
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