From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Wed, 1 May 2002 17:23:23 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Wed, 1 May 2002 17:23:22 -0400 Received: from quechua.inka.de ([212.227.14.2]:15163 "EHLO mail.inka.de") by vger.kernel.org with ESMTP id ; Wed, 1 May 2002 17:23:22 -0400 From: Bernd Eckenfels To: linux-kernel@vger.kernel.org Subject: Re: raid1 performance In-Reply-To: <20020501130127.A10936@borg.org> X-Newsgroups: ka.lists.linux.kernel User-Agent: tin/1.5.8-20010221 ("Blue Water") (UNIX) (Linux/2.0.39 (i686)) Message-Id: Date: Wed, 1 May 2002 23:23:23 +0200 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org In article <20020501130127.A10936@borg.org> you wrote: > 1. Does the OS even know where the heads are in a modern IDE disk? > 2. Is "closer" any more finely grained than a binary > positioned/not-positioned? > And I guess another question: How much does RAID 1 help and under what > kinds of usage? No, you just distribute the ready round robin, this means each disk has only half the seeks it had before. As long as you do not spread continous blocks (readahead) stats are good you actually reduce overall seeks. This helps actually even if no seek is involved because of the fact that you need to wait for the begin of a track to read it. Greetings Bernd