Re: [RESEND] [PATCH] readahead:add blk_run_backing_dev

[Vladislav Bolkhovitin]

Vladislav Bolkhovitin, on 07/10/2009 12:43 PM wrote:
> Ronald Moesbergen, on 07/10/2009 10:32 AM wrote:
> > > I've also long ago noticed that reading data from block devices is slower
> > > than from files from mounted on those block devices file systems. Can
> > > anybody explain it?
> > >
> > > Looks like this is strangeness #2 which we uncovered in our tests (the first
> > > one was earlier in this thread why the context RA doesn't work with
> > > cooperative I/O threads as good as it should).
> > >
> > > Can you rerun the same 11 tests over a file on the file system, please?
> > I'll see what I can do. Just te be sure: you want me to run
> > blockdev-perftest on a file on the OCFS2 filesystem which is mounted
> > on the client over iScsi, right?
>
> Yes, please.

Forgot to mention that you should also configure your backend storage as 
a big file on a file system (preferably, XFS) too, not as direct device, 
like /dev/vg/db-master.

Thanks,
Vlad

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