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

[Vladislav Bolkhovitin <vst@vlnb.net>]

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