From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sitsofe Wheeler Subject: Re: Slow writing of dirty data (bcache) Date: Mon, 10 Mar 2014 20:56:20 +0000 Message-ID: <20140310205612.GA19912@sucs.org> References: <531DE9A5.90801@nuclearwinter.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from silver.sucs.swan.ac.uk ([137.44.10.1]:55284 "EHLO silver.sucs.swan.ac.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754739AbaCJU4W (ORCPT ); Mon, 10 Mar 2014 16:56:22 -0400 Content-Disposition: inline In-Reply-To: <531DE9A5.90801@nuclearwinter.com> Sender: linux-bcache-owner@vger.kernel.org List-Id: linux-bcache@vger.kernel.org To: Larkin Lowrey Cc: linux-bcache@vger.kernel.org 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)... -- Sitsofe | http://sucs.org/~sits/