From mboxrd@z Thu Jan 1 00:00:00 1970 From: John Robinson Subject: Re: RAID without superblock Date: Mon, 20 Apr 2009 00:33:08 +0100 Message-ID: <49EBB4B4.40102@anonymous.org.uk> References: <20090419114743.GA29195@lazy.lzy> <20090419210200.GA6942@lazy.lzy> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20090419210200.GA6942@lazy.lzy> Sender: linux-raid-owner@vger.kernel.org To: Piergiorgio Sartor Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids On 19/04/2009 22:04, Piergiorgio Sartor wrote: >> Why would you want a RAID-1 without superblock. I generally >> consider that a legacy configuration. > > Ah! I was thinking about it as a method to > build a RAID with an already existing disk > or partition, which cannot be modified. Well, something somewhere is going to have to change; at the very least you're going to have to stop whatever's using the filesystem, unmount it, do whatever to create the new RAID-1 incorporating the original disc, and remount the filesystem now on the new md device. So instead you could create a new RAID-1 md device with (a superblock and) one disc missing, create a filesystem on it, stop your original filesystem, copy its contents to the new md device, mount it, and add the original disc into the new md device. If you've too much data to be able to afford the downtime copying, use rsync with the appropriate options while the filesystem's still in use, then again after it's been stopped; the second copy will complete far faster than the full copy. Cheers, John.