From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paul Clements Subject: Re: multi-hosting support for carrier grade Linux Date: Tue, 05 Apr 2005 17:50:23 -0400 Message-ID: <4253081F.6000901@steeleye.com> References: <20050405204155.GA32724@blade.az.mvista.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20050405204155.GA32724@blade.az.mvista.com> Sender: linux-raid-owner@vger.kernel.org To: Dave Jiang Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids Dave Jiang wrote: > I'm attempting to implement multihost support of the MD for environments > such as carrier grade Linux. Multihost support allows the RAID array to > be claimed by a particular host via a unique ID (unique SCSI host ID, > FibreChannel WWN, or geographical address of a chassis blade. That way > another host that can access the disks do not claim the same disks that > are used by the RAID array. Why not just use SCSI reservations? > I would like to store a 64bit unique ID on the > superblock of the device. The least intrusive way IMHO to do this is > implementing the feature via the management app such as mdadm in > userland. However, it seems that after I instruct the kernel to create the MD array via mdadm, the kernel starts out with a blank superblock and clobbers the If you write a valid superblock to the disk and then assemble the array, the superblock doesn't get clobbered. > data I have stored on the superblock via mdadm. Would it be acceptable > to modify the kernel such that the unique ID info is preserved during > the creation of the superblock by the kernel? Example patch follows: As for adding additional fields to the various superblock formats, you'd have to ask Neil if he's open to that. -- Paul