From mboxrd@z Thu Jan  1 00:00:00 1970
From: Mike Snitzer <snitzer@redhat.com>
Subject: Re: [PATCH RFC 0/2] dm-zoned: add cache device
Date: Mon, 23 Mar 2020 11:15:38 -0400
Message-ID: <20200323151538.GA27573@redhat.com>
References: <20200323150352.107826-1-hare@suse.de>
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To: Hannes Reinecke <hare@suse.de>
Cc: Damien LeMoal <damien.lemoal@wdc.com>, Johannes Thumshirn <jth@kernel.org>, dm-devel@redhat.com
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On Mon, Mar 23 2020 at 11:03am -0400,
Hannes Reinecke <hare@suse.de> wrote:

> Hi Damien,
> 
> as my original plan to upgrade bcache to work for SMR devices
> turned out to be more complex than anticipated I went for the
> simpler approach and added a 'cache' device for dm-zoned.
> It is using a normal device (eg '/dev/pmem0' :-), split it
> into zones of the same size of the original SMR device, and
> makes those 'virtual' zones avialable to dm-zoned in a similar
> manner than the existing 'random write' zoned.
> 
> The implementation is still a bit rough (one would need to add
> metadata to the cache device, too), but so far it seems to work
> quite well; still running after copying 300GB of data back and forth.
> 
> As usual, comments and reviews are welcome.

Not seeing why this needs to be so specialized (natively implemented in
dm-zoned).  Did you try stacking dm-writecache on dm-zoned?

Mike