From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andreas Dilger Subject: Re: Proposed Enhancements to MD Date: Tue, 13 Jan 2004 10:13:50 -0700 Sender: linux-raid-owner@vger.kernel.org Message-ID: <20040113171350.GI1437@schnapps.adilger.int> References: <40036902.8080403@adaptec.com> <20040113081932.A721@lists.us.dell.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7BIT Return-path: In-reply-to: <20040113081932.A721@lists.us.dell.com> Content-Disposition: inline To: Matt Domsch Cc: Scott Long , linux-raid@vger.kernel.org, linux-kernel@vger.kernel.org List-Id: linux-raid.ids On Jan 13, 2004 08:19 -0600, Matt Domsch wrote: > On Mon, Jan 12, 2004 at 08:41:54PM -0700, Scott Long wrote: > > - DDF Metadata support: Future products will use the 'DDF' on-disk > > metadata scheme. These products will be bootable by the BIOS, but > > must have DDF support in the OS. This will plug into the abstraction > > mentioned above. > > For those unfamiliar with DDF (Disk Data Format), it is a Storage > Networking Industry Association (SNIA) project ("Common RAID DDF > TWG"), designed to provide a single metadata format to be used by all > the RAID vendors (hardware and software alike). It removes vendor > lock-in by having a metadata format that all can use, thus in theory > you could move disks from an Adaptec hardware RAID controller to an > LSI software RAID solution without reformatting the disks or touching > your file systems in any way. Dell has been championing the DDF > concept for quite a while, and is driving vendors from which we > purchase RAID solutions to use DDF instead of their own individual > metadata formats. > > I haven't seen the spec yet myself, but I'm lead to believe that > DDF allows for multiple logical drives to be created across a single > set of disks (e.g. a 10GB RAID1 LD and a 140GB RAID0 LD together on > two 80GB spindles), as well as whole disks be used. It has a > mechanism to support reconstruction checkpointing, so you don't have > to restart a reconstruct from the beginning after a reboot, but from > where you left off. And other useful features too that you'd expect > in a common RAID solution. So, why not use EVMS and/or Device Mapper to read the DDF metadata and set up the mappings that way? Cheers, Andreas -- Andreas Dilger http://sourceforge.net/projects/ext2resize/ http://www-mddsp.enel.ucalgary.ca/People/adilger/