From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262799AbTJWIMs (ORCPT ); Thu, 23 Oct 2003 04:12:48 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261705AbTJWIMm (ORCPT ); Thu, 23 Oct 2003 04:12:42 -0400 Received: from atrey.karlin.mff.cuni.cz ([195.113.31.123]:35226 "EHLO atrey.karlin.mff.cuni.cz") by vger.kernel.org with ESMTP id S261687AbTJWIMi (ORCPT ); Thu, 23 Oct 2003 04:12:38 -0400 Date: Sun, 19 Oct 2003 11:25:20 +0200 From: Pavel Machek To: Jakob Oestergaard , kernel list Subject: Re: Software RAID5 with 2.6.0-test Message-ID: <20031019092519.GO1659@openzaurus.ucw.cz> References: <1065690658.10389.19.camel@slurv> <20031017192419.GG8711@unthought.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20031017192419.GG8711@unthought.net> User-Agent: Mutt/1.3.27i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Hi! > Now that I'm posting anyway - I thought of a plus for the HW RAID > controllers (hey, they're way behind on the scoreboard so far, so I > might as well be a gentleman and give them a point or two): > *) Battery backed write cache > > This will allow the controller to say 'ok I'm done with your sync()', > way before the data actually reaches the disk platters. For some Well, this would mean not only battery-backed controller, but battery-backed drives, too. (Unless you want to assume that memory-backup-battery never goes empty). > While on that topic: SDRAM PCI cards with battery backup can be had > relatively cheap up to at least a few gigabytes. It'd be pretty cool to > have the kernel recognize that for buffer storage. I could see the fun > in doing half a million random writes and a sync(), and having the > system tell me it's done the microsecond I issue the sync(). Sync would still take some time as it still makes sense to do writeback... Main memory is still faster than PCI. Pavel -- Pavel Written on sharp zaurus, because my Velo1 broke. If you have Velo you don't need...