From mboxrd@z Thu Jan 1 00:00:00 1970 From: Brad Campbell Subject: Re: full ssd for bcache or part? Date: Thu, 24 Oct 2013 10:24:56 +0800 Message-ID: <526884F8.4080000@fnarfbargle.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-bcache-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Matthew Patton , Vasiliy Tolstov , linux-bcache-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-bcache@vger.kernel.org On 10/24/2013 12:15 AM, Matthew Patton wrote: > 25 to 30 percent reserve is strongly recommended for any write heavy workload. The performance improvement will blow your mind. > > A 240GB drive is a 256 with 7 percent reserve. Partition your device to 185 GB. I thought (and maybe I'm wrong) that a good chunk of reserved space was essential to allow the drive to efficiently manage its read-modify-write cycles. It was my understanding that bcache was explicitly designed to fill erase block sized chunks sequentially and discard them in whole units, negating the requirement for the drive to actually perform RMW cycles and therefore negating the requirement for the extra free space. Have I got it wrong? Regards, Brad