From mboxrd@z Thu Jan  1 00:00:00 1970
From: Kumar amit mehta <gmate.amit@gmail.com>
Subject: Re: dm-cache: dirty state of blocks in writethrough mode
Date: Wed, 24 Jul 2013 09:02:20 -0400
Message-ID: <20130724130220.GC6963@gmail.com>
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On Wed, Jul 24, 2013 at 07:05:59PM +0200, Heinz Mauelshagen wrote:
> dm-cache maintains it's own metadata keeping track of any cached
> blocks properties
> such as a block being dirty in case of writeback.
> 
> If any write in writeback mode hits a cache block, the cache metadata will
> reflect that dirty state before the write's being reported to the
> application.
> 
> After a crashed system rebooted, that information is available to flush a
> dirty block out on eviction.

Ahh, so It is the metadata device. Maybe overkill, but is it
possible to keep redundant copies of this metadata, like user space
utilities such as LVM2 does?

!!amit