From mboxrd@z Thu Jan  1 00:00:00 1970
From: Dallas Clement <dallas.a.clement@gmail.com>
Subject: Re: best base / worst case RAID 5,6 write speeds
Date: Mon, 14 Dec 2015 14:55:09 -0600
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To: Mark Knecht <markknecht@gmail.com>
Cc: Phil Turmel <philip@turmel.org>, John Stoffel <john@stoffel.org>, Linux-RAID <linux-raid@vger.kernel.org>
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On Mon, Dec 14, 2015 at 2:40 PM, Mark Knecht <markknecht@gmail.com> wrote:
>
>
> On Mon, Dec 14, 2015 at 12:14 PM, Dallas Clement
> <dallas.a.clement@gmail.com> wrote:
>>
>> <SNIP>
>>
>> Hi Phil,  I ran blktrace while writing with dd to a RAID 5 device with
>> 12 disks.  My chunk size is 128K.  So I set my block size to 128K *
>> (12-2) = 1280k.   Here is the dd command I ran.
>
> Just curious but for my own knowledge if it's RAID5 why is it 12-2?
>
> - Mark

> Just curious but for my own knowledge if it's RAID5 why is it 12-2?

Shouldn't be.  It should have been 12-1 or writing 1408k.  Boy do I
feel dumb.  Anyhow, when writing this value, no more RMWs.   Yay!