From mboxrd@z Thu Jan 1 00:00:00 1970 From: Matt Domsch Subject: Re: Proposed Enhancements to MD Date: Tue, 13 Jan 2004 08:19:32 -0600 Sender: linux-raid-owner@vger.kernel.org Message-ID: <20040113081932.A721@lists.us.dell.com> References: <40036902.8080403@adaptec.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <40036902.8080403@adaptec.com>; from scott_long@adaptec.com on Mon, Jan 12, 2004 at 08:41:54PM -0700 To: Scott Long Cc: linux-raid@vger.kernel.org, linux-kernel@vger.kernel.org List-Id: linux-raid.ids 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. DDF is quickly becoming important to RAID and system vendors, and I welcome Adaptec's work to implement DDF support on Linux. Thanks, Matt -- Matt Domsch Sr. Software Engineer, Lead Engineer Dell Linux Solutions www.dell.com/linux Linux on Dell mailing lists @ http://lists.us.dell.com