From mboxrd@z Thu Jan  1 00:00:00 1970
From: thornber@redhat.com
Subject: Re: How to use dm-cache-target?
Date: Mon, 11 Mar 2013 10:31:53 +0000
Message-ID: <20130311103152.GA5038@raspberrypi>
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On Mon, Mar 11, 2013 at 10:28:07AM +0800, majianpeng wrote:
> Hi all,
>     I am trying to use dm-cache-target on raid5.But i met a question.
> 
>  Supposed: /dev/sdb1(5GB) is metadata; /dev/sdb2(20GB) is cache;/dev/md0 is raid5.
> 
> 1:sutup my_cache
> dmsetup create my_cache --table '0 41943040 cache /dev/sdb1 /dev/sdb2 /dev/md0 131072 1 writethrough default 0'

41943040 - This is 20G, you should use the size of /dev/md0 in sectors

Also I think your block size is way too big, try 2048 rather tha 131072.

> BTW, for dm-cache is it support plug-and-play?

No idea what you mean.

- Joe