From mboxrd@z Thu Jan 1 00:00:00 1970 From: =?UTF-8?Q?Jure_Erzno=C5=BEnik?= Subject: Cache everything Date: Fri, 30 Dec 2016 09:38:21 +0100 Message-ID: Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Return-path: Received: from mail-yw0-f179.google.com ([209.85.161.179]:35674 "EHLO mail-yw0-f179.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751785AbcL3IiW (ORCPT ); Fri, 30 Dec 2016 03:38:22 -0500 Received: by mail-yw0-f179.google.com with SMTP id v81so120005364ywb.2 for ; Fri, 30 Dec 2016 00:38:22 -0800 (PST) Sender: linux-bcache-owner@vger.kernel.org List-Id: linux-bcache@vger.kernel.org To: linux-bcache@vger.kernel.org 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