From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stan Hoeppner Subject: Re: RAID-0/5/6 performances Date: Fri, 06 Dec 2013 03:24:18 -0600 Message-ID: <52A197C2.1090805@hardwarefreak.com> References: <20131205192454.GA5695@lazy.lzy> Reply-To: stan@hardwarefreak.com Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20131205192454.GA5695@lazy.lzy> Sender: linux-raid-owner@vger.kernel.org To: Piergiorgio Sartor , linux-raid@vger.kernel.org List-Id: linux-raid.ids On 12/5/2013 1:24 PM, Piergiorgio Sartor wrote: > The "stripe_cache_size" was set to the max 32768. You don't want to set this so high. Doing this will: 1. Usually decrease throughput 2. Eat a huge amount of memory. With 5 drives: ((32768*4096)*5)/1048576 = 640 MB RAM consumed for the stripe buffer For 5 or fewer pieces of spinning rust a value of 2048 or less should be sufficient. Test 512, 1024, 2048, 4096, and 8192. You should see your throughput go up and then back down. Find the sweet spot and use that value. If two of these yield throughput within 5% of one another, use the lower value as it eats less RAM. -- Stan