From mboxrd@z Thu Jan 1 00:00:00 1970 From: Keld =?iso-8859-1?Q?J=F8rn?= Simonsen Subject: Re: raid10 vs raid5 - strange performance Date: Sun, 30 Mar 2008 10:55:28 +0200 Message-ID: <20080330085528.GC17756@rap.rap.dk> References: <20080325233649.GA632@rap.rap.dk> <20080326072416.GA8674@rap.rap.dk> <20080326192935.GB18621@rap.rap.dk> <47EAACAB.7070203@tmr.com> <47EEA5BB.5080106@tmr.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <47EEA5BB.5080106@tmr.com> Sender: linux-raid-owner@vger.kernel.org To: Bill Davidsen Cc: Christian Pernegger , Linux RAID List-Id: linux-raid.ids On Sat, Mar 29, 2008 at 04:25:31PM -0400, Bill Davidsen wrote: > Christian Pernegger wrote: > > The md raid10,f2 generally has modest write performance, if U is a > single drive speed, write might range between 1.5U to (N-1)/2*U > depending on tuning. Read speed is almost always (N-1)*U, which is great > for many applications. Playing with chunk size, chunk buffers, etc, can > make a large difference in write performance. Hmm, I have other formulae for this. raid10,f2 write speed would rather be U*N/2, and read speed be U*N - possibly enhanced by also having bigger chunks than on a regular non-raid disk, and enhanced by lower access times. The formulae are bothe for sequential and random reads. Best regards keld