From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bernd Schubert Subject: Re: raid resync speed Date: Thu, 20 Mar 2014 16:36:36 +0100 Message-ID: <532B0B04.5030602@fastmail.fm> References: <532AFCC8.6080902@hardwarefreak.com> <532B0ABC.5040604@fastmail.fm> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <532B0ABC.5040604@fastmail.fm> Sender: linux-raid-owner@vger.kernel.org To: stan@hardwarefreak.com, Jeff Allison , linux-raid@vger.kernel.org List-Id: linux-raid.ids On 03/20/2014 04:35 PM, Bernd Schubert wrote: >> >> Yes. The article gives 16384 and 32768 as examples for >> stripe_cache_size. Such high values tend to reduce throughput instead >> of increasing it. Never use a value above 2048 with rust, and 1024 is >> usually optimal for 7.2K drives. Only go 4096 or higher with SSDs. In >> addition, high values eat huge amounts of memory. The formula is: >> > > Why should the stripe-cache size differ between SSDs and rotating disks? > Did you ever try to figure out yourself why it got slower with higher > values? I profiled that in the past and it was a CPU/memory limitation - > the md thread went to 100%, searching for stripe-heads. Sorry, I forgot to write 'cpu usage', so it went to 100% cpu usage. > > So I really wonder how you got the impression that the stripe cache size > should have different values for differnt kinds of drives. > > > Cheers, > Bernd >