From mboxrd@z Thu Jan 1 00:00:00 1970 From: Graeme Sheppard Subject: Re: Patent or not patent a new idea Date: Tue, 26 Jun 2007 16:22:45 +1200 Message-ID: <46809495.6000109@rillion.net> References: <46803772.7020408@rillion.net> <46806CCB.6020708@rillion.net> <18048.30679.872740.744997@notabene.brown> <468085E9.70804@rillion.net> <18048.35410.896207.686311@notabene.brown> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org To: Neil Brown Return-path: Received: from server.rillion.net ([207.210.78.215]:42424 "EHLO rillion.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750828AbXFZEXE (ORCPT ); Tue, 26 Jun 2007 00:23:04 -0400 In-Reply-To: <18048.35410.896207.686311@notabene.brown> Sender: linux-fsdevel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org Neil Brown wrote: > ??? > (reads original description in more detail). > > So... the filesystem images are identical in both copies, and the > "interesting" bit is that the image is just a file on some filesystem. > > So could I implement your idea by: > > dd if=/dev/zero of=/1/bigfile count=lotsandlots > dd if=/dev/zero of=/2/bigfile count=lotsandlots > losetup /dev/loop1 /1/bigfile > losetup /dev/loop2 /2/bigfile > mdadm -C /dev/md0 --level=raid1 --raid-disks=2 /dev/loop1 /dev/loop2 > mkfs /dev/md0 > mount /dev/md2 /space > > ?? > > Why would you bother? Well, I do it a lot of code testing, but I > would be hard pressed to make a case for that sort of config in > production. Thanks for the brief howto there. I'll install the mdadm suite and experiment. It seems like a userspace driver? > You said: >> 1) the disks need >> not be the same size or from the same manufacturer; 2) the supporting code >> would be cross-platform. > > md/raid already works happily with different sized drives from > different manufacturers (for raid1, it only uses as much space as the smaller > drive provides, For raid0 it uses it all). > I don't know what you mean by '2'. 2 meant in the way that a driver for a PC raid card is not much use on a Sparc. > So I still cannot see anything particularly new. What am I missing? I think it's what I missed. Thanks for the heads-up. If the above is a good technique it could suit me well.