[dm-devel] Re: IO scheduler based IO controller V10

[Ryo Tsuruta <ryov valinux co jp>]

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?