Re: RAID5 question.

[djani22@dynamicweb.hu]

Thanks a lot for you, and Raz!

The raw devices readahead I already set with the hdparm, and
/sys/block/*/queue/read_ahead_kb, but the md device is only changeable with
blockdev. :-)
I dont use lvm, because it is too slow for me....

But unfortunately the problem is still here for me. :(
I continue searching the bottleneck...

Thanks!

Janos

----- Original Message -----
From: "David Greaves" <david@dgreaves.com>
To: "Raz Ben Jehuda" <razb@bitband.com>
Cc: <djani22@dynamicweb.hu>; <linux-raid@vger.kernel.org>
Sent: Thursday, August 04, 2005 4:56 PM
Subject: Re: RAID5 question.


> And notice you can apply different readahead to:
> The raw devices (/dev/sda)
> The md device (/dev/mdX)
> Any lvm device (/dev/lvm_name/lvm_device)
>
> David
>
> Raz Ben Jehuda wrote:
>
> >read the blockdev man page
> >
> >On Thu, 2005-08-04 at 16:06 +0200, djani22@dynamicweb.hu wrote:
> >
> >
> >>Hi list, Neil!
> >>
> >>I have a little question because I'v got some performance problem...
> >>Is the RAID5 do any type of headahead with the default config?
> >>It is possible to disable the readahead? (if it is.)
> >>Or just the io_sched do that on the disks?
> >>
> >>How can I disable the whole headahead on top of the RAID5 array?
> >>
> >>The RAID5 can do multiple small (<4kb) reads of disks for the
multithreaded
> >>read requests?
> >>(chunk size is 32k)
> >>
> >>Thanks for helping!
> >>
> >>Janos
> >>
> >>-
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> >>
> >>
>
>
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