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Date: Fri, 11 Sep 2015 13:51:05 +0100
From: Joe Thornber <thornber@redhat.com>
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Subject: Re: [linux-lvm] Strange dm-cache activity at startup
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On Thu, Sep 10, 2015 at 11:30:27AM +0200, Stefan Ring wrote:
> Is this normal/expected? What does it do? Why does it write back huge
> amounts of data to the HDD after each system start?

No, this is not expected.  The most likely cause is your system was
not shutdown cleanly so dm-cache has no choice but to assume all
blocks are dirty and need writing back.  Make sure your volumes are
being deactivated as part of shutdown.

- Joe