On Mon, Mar 10, 2014 at 11:34:45AM -0500, Larkin Lowrey wrote:

has 160+MB of dirty data. The dirty data is being written at a rate of 1
page per second (8 sectors). At this rate it'll take 11 hrs to finish. I
like to keep this array spun down when inactive but the drives can't
spin down since they're being written to once a second.

This never happened when running 3.12.7. Is there anything I can do
about this?

I believe this is intended behaviour - as the cache approaches the
writeback_percent level of fullness the rate of writeback will increase.
It is possible to override the writeback_rate by echoing a new value
into it but it will also change itself so you may find the rate falls
again...  Perhaps that can be avoided by echoing 0 into
writeback_percent too (see
http://evilpiepirate.org/git/linux-bcache.git/tree/Documentation/bcache.txt?h=bcache-dev#n265)...

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