From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Landmann Subject: Re: RAID 5 doesn't scale Date: Wed, 3 Apr 2013 21:29:30 +0000 (UTC) Message-ID: References: <515C2C3C.3020400@hardwarefreak.com> <515C73B3.5060704@arcor.de> <515C9E05.9070300@hardwarefreak.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Return-path: Sender: linux-raid-owner@vger.kernel.org To: linux-raid@vger.kernel.org List-Id: linux-raid.ids > If you're running the tests for multiple minutes and many tens of GBs at > a time, then this slowdown is due to garbage collection, not stripe > cache sizing. You are right. I wrote about that in another post. > > You are not performing proper testing methodologies, and you're jumping > to conclusions way too quickly, and likely incorrectly. See above. > > If you're not familiar with SSD garbage collection then you must learn > about it. It will affect everything you do with SSDs, especially when > doing these kinds of tests where you're writing huge amounts of data to > the flash cells. Wear leveling, part of garbage collection, > dramatically slows down SSD throughput. And when you're pushing this > much data, TRIM won't help. It'll actually slow the SDDs down even more. In a shortage of time i was to fast .. I'm sorry for the trouble but at least some people and i could learn something about md :) Peter