From mboxrd@z Thu Jan 1 00:00:00 1970 From: Neil Brown Subject: Re: Patent or not patent a new idea Date: Tue, 26 Jun 2007 13:38:58 +1000 Message-ID: <18048.35410.896207.686311@notabene.brown> References: <46803772.7020408@rillion.net> <46806CCB.6020708@rillion.net> <18048.30679.872740.744997@notabene.brown> <468085E9.70804@rillion.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org To: Graeme Sheppard Return-path: Received: from mx2.suse.de ([195.135.220.15]:51106 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752223AbXFZDjI (ORCPT ); Mon, 25 Jun 2007 23:39:08 -0400 In-Reply-To: message from Graeme Sheppard on Tuesday June 26 Sender: linux-fsdevel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org On Tuesday June 26, nodes@rillion.net wrote: > Neil Brown wrote: > > > > Sounds a lot like "RAIF" - ask google for details. > > I did not know about RAIF. RAIF "merges" separate filesystems? That is a > good idea in itself. > > My idea is for driver that provides a filesystem from image files it > controls. Because it knows these resources it uses access in tandem to > attain performance. ??? (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. 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'. So I still cannot see anything particularly new. What am I missing? NeilBrown