From mboxrd@z Thu Jan 1 00:00:00 1970 From: Killian De Volder Subject: Re: Cache everything Date: Fri, 30 Dec 2016 09:58:19 +0100 Message-ID: <586621AB.7040208@megasoft.be> References: Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Return-path: Received: from relay6-d.mail.gandi.net ([217.70.183.198]:33611 "EHLO relay6-d.mail.gandi.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752412AbcL3I6Y (ORCPT ); Fri, 30 Dec 2016 03:58:24 -0500 Received: from mfilter27-d.gandi.net (mfilter27-d.gandi.net [217.70.178.155]) by relay6-d.mail.gandi.net (Postfix) with ESMTP id 6FF55FB877 for ; Fri, 30 Dec 2016 09:58:21 +0100 (CET) Received: from relay6-d.mail.gandi.net ([IPv6:::ffff:217.70.183.198]) by mfilter27-d.gandi.net (mfilter27-d.gandi.net [::ffff:10.0.15.180]) (amavisd-new, port 10024) with ESMTP id TFnIeTC3NDrM for ; Fri, 30 Dec 2016 09:58:19 +0100 (CET) Received: from [172.17.0.70] (host-e0vuwqj.cbn1.zeelandnet.nl [213.34.255.70]) (Authenticated sender: killian.de.volder@megasoft.be) by relay6-d.mail.gandi.net (Postfix) with ESMTPSA id AF513FB8A1 for ; Fri, 30 Dec 2016 09:58:19 +0100 (CET) In-Reply-To: Sender: linux-bcache-owner@vger.kernel.org List-Id: linux-bcache@vger.kernel.org To: linux-bcache@vger.kernel.org Also check congested_write_threshold_us, if the SSD is "congested" it bypasses it to speedup writes. Killian De Volder On 30-12-16 09:38, Jure Erznožnik wrote: > I have a large array sitting in my server containing a bit of data > that is used ofter and a lot of data that is used rarely. > My goal is to make the platters spin up as rarely as possible while > bcache handles most of the requests to the array. > > I have set the disks spin-down time to 15 minutes so that during > high-activity periods they don't cycle power states too much. > > I have set bcache parameters such: > cache_mode - writeback > readahead - 0 > sequential_cutoff - 0 > writeback_delay - 3600 (one hour) > writeback_percent - 40 (won't go higher) > > I was hoping that this would make bcache cache everything leaving the > array practically untouched for an hour. However, stats_hour/bypassed > still shows megabytes of bypassed data and a cache_hit ratio of ~50% > even when I'm working ONLY with the frequently accessed data portion > (some 20% of total cache capacity). Also tiny writes are being made to > the array despite writeback_delay not expiring. > > What other parameter am I forgetting to achieve what I want? > > Thanks, > Jure > -- > To unsubscribe from this list: send the line "unsubscribe linux-bcache" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html >