From mboxrd@z Thu Jan  1 00:00:00 1970
From: Paul Clements <paul.clements@steeleye.com>
Subject: Re: question about bitmaps and dirty percentile
Date: Mon, 03 Aug 2009 16:30:14 -0400
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Matthias Urlichs wrote:
> On Fri, 31 Jul 2009 14:09:06 -0500, Jon Nelson wrote:
> 
>>> The bitmap never gets cleared unless all disks in the array are in
>>> sync.
>> Well, that sucks. What is the reasoning behind that?
> 
> There's only one bitmap per device. If the bits get cleaned writing to 
> disk #2, then the system would forget that they still need to be written 
> to disk #3.

Right, and that decision was made for efficiency and simplicity of 
design. Having a bitmap per pair of component disks would be inefficient 
and very complicated. You could stack raid1's if you absolutely had to 
have that type of functionality.

--
Paul