From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Fri, 24 Aug 2001 16:22:11 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Fri, 24 Aug 2001 16:22:01 -0400 Received: from islay.mach.uni-karlsruhe.de ([129.13.162.92]:22182 "EHLO mailout.plan9.de") by vger.kernel.org with ESMTP id ; Fri, 24 Aug 2001 16:21:48 -0400 Date: Fri, 24 Aug 2001 22:22:02 +0200 From: To: Neil Brown Cc: linux-kernel@vger.kernel.org Subject: Re: software raid does not do parallel reads under 2.4? Message-ID: <20010824222202.B12903@fuji.laendle> Mail-Followup-To: Neil Brown , linux-kernel@vger.kernel.org In-Reply-To: <20010823234218.B12873@cerebro.laendle> <15238.11161.492557.264988@notabene.cse.unsw.edu.au> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <15238.11161.492557.264988@notabene.cse.unsw.edu.au> X-Operating-System: Linux version 2.4.8-ac8 (root@cerebro) (gcc version 3.0.1) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Aug 24, 2001 at 08:25:29PM +1000, Neil Brown wrote: > For raid0, the md driver just redirects requests to the right drive. > It doesn't explicitly serialise or parallelise anything. 2.4 works in > exactly the same was as 2.2. then why is 2.2 so much faster? > With a 2MB chunksize, I would expect a linear read to touch just one > drive at a time. why? i read 8mb cvhunks a time (see the dd) so it should read 3x2mb chunks easily. anyway, i get the same throughput with 64k, 16k etc.. chunksize. > With a 4K chunk size, I suspect that an linear read would read from > all the drives in parallel. maybe, but it's still exactly as fast: 30mb/s, which is slower than one drive can do. -- -----==- | ----==-- _ | ---==---(_)__ __ ____ __ Marc Lehmann +-- --==---/ / _ \/ // /\ \/ / pcg@goof.com |e| -=====/_/_//_/\_,_/ /_/\_\ XX11-RIPE --+ The choice of a GNU generation | |