From mboxrd@z Thu Jan 1 00:00:00 1970 From: John Robinson Subject: Re: Superblock V 1.2 Date: Sun, 07 Nov 2010 21:39:03 +0000 Message-ID: <4CD71C77.4030400@anonymous.org.uk> References: <20101107191507.GA31052@cons.org> <20101107210852.GA77472@cons.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20101107210852.GA77472@cons.org> Sender: linux-raid-owner@vger.kernel.org To: Martin Cracauer Cc: Leslie Rhorer , linux-raid@vger.kernel.org List-Id: linux-raid.ids On 07/11/2010 21:08, Martin Cracauer wrote: > Thanks, Leslie, > > Leslie Rhorer wrote on Sun, Nov 07, 2010 at 03:03:39PM -0600: >> >>> Can I read that array if I ever connect the machine to an older >>> kernel/mdadm? >> >> That depends on just how old. The new superblocks have been >> supported for quite some time. Worst case you will need to upgrade the old >> kernel to a newer one. > > Is mdadm actually involved? If I have a new enough kernel but an old > mdadm, will the kernel code alone be enough to start the array? > > I guess it should since it can start the arrays at boot time with no > mdadm involved. That's the other difference between 0.90 and 1.x metadata. In-kernel auto-assembly is only available for 0.90, and Neil Brown has made it clear that there will never be in-kernel auto-assembly for 1.x, and explained at length why. You need mdadm to start 1.x arrays, in your initrd if your root filesystem is on such an array. All modern distros create suitable initrds automatically. We are moving towards having array assembly handled by udev invoking mdadm as devices are discovered. Cheers, John.