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Date: Fri, 30 May 2014 07:53:45 -0400
From: Mike Snitzer <snitzer@redhat.com>
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Subject: Re: [linux-lvm] Testing the new LVM cache feature
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To: "Richard W.M. Jones" <rjones@redhat.com>
Cc: Zdenek Kabelac <zkabelac@redhat.com>, thornber@redhat.com, LVM general discussion and development <linux-lvm@redhat.com>

On Thu, May 29 2014 at  5:58pm -0400,
Mike Snitzer <snitzer@redhat.com> wrote:
 
> BTW, this is all with a eye toward realizing the optimization that
> dm-cache provides for origin blocks that were discarded (like I said
> before dm-cache doesn't promote from the origin if the corresponding
> block was marked for discard).  So you don't _need_ to do any of
> this.. purely about trying to optimize a bit more.

And if you do make use of discards, you should have this stable fix
applied to your kernel:

https://git.kernel.org/cgit/linux/kernel/git/device-mapper/linux-dm.git/commit/?h=for-linus&id=f1daa838e861ae1a0fb7cd9721a21258430fcc8c