Re: Raid 5 Read performance

Hi Majed & All,

Yes we two are working together. Actually we found a change in md/raid5.c
file in the function sync_request() it restricts the numbers, the kernel
2.6.27 has code like this

while(unlikely(!handle_stripe(sh, NULL)))
                ;
 But in kernel 2.6.21 it simply the handle_stripe(sh, NULL) call.

Can anybody tell me the necessity of the change, and why it reduces the
numbers. Any comments is very helpful for me to analyze the driver further.


Thanks,
Satha.

--- On Fri, 11/9/09, Majed B. <majedb@gmail.com> wrote:

From: Majed B. <redacted>
Subject: Re: Raid 5 Read performance
To: "Koti" <redacted>
Cc: linux-raid@vger.kernel.org
Date: Friday, 11 September, 2009, 1:47 AM

Someone else has already emailed the mailing list about this. Are you
two running an assignment or something?!

Check the mailing list archive for whatever people have already replied
with.

On Thu, Sep 10, 2009 at 11:07 PM, Koti[off-list ref] wrote:

quoted

Hi All

I am trying measure the RAID 5 Read numbers on linux kernel-2.6.21 and
kernel 2.6.27 the numbers are lower on later kernel (2.6.27). Iam
measuring
the numbers using "time dd" command (4GB ). Is any valid reason for this,
or
Am missing anything in the process. Can anybody help me in analyze this
problem.

Thanks,
Koti

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--
       Majed B.

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