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Date: Mon, 8 Feb 2016 09:17:06 +0000
From: Joe Thornber <thornber@redhat.com>
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Subject: Re: [linux-lvm] lvmcache performance
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To: LVM general discussion and development <linux-lvm@redhat.com>

On Sun, Feb 07, 2016 at 10:43:30AM -0800, Nikolaus Rath wrote:
> Is that the wrong expectation? But even then, shouldn't I at least see
> some improvement?

Firstly, if you have the latest software, I suggest you switch to the
smq cache policy which is generally out performing the old mq policy
substantially.

Secondly, I think you may need to reset your expectations a bit.
dm-cache is a slow moving cache.  It monitors IO, detectings hotspots
on the disk and then 'promotes' those regions to the SSD.  You may
find that the reads that occur during a boot, occur only infrequently
once the system is booted.

- Joe