From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Werner John MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Message-ID: <15226.31281.143943.166236@rigel.oswf.de> Date: Wed, 15 Aug 2001 15:33:37 +0200 (MEST) Subject: Re: [linux-lvm] Adding a mirror after-the-fact In-Reply-To: <20010815091329.A29902@linux.com> References: <20010814171159.B28266@linux.com> <20010815105623.A29693@sistina.com> <20010815091329.A29902@linux.com> Sender: linux-lvm-admin@sistina.com Errors-To: linux-lvm-admin@sistina.com Reply-To: linux-lvm@sistina.com List-Help: List-Post: List-Subscribe: , List-Unsubscribe: , List-Archive: List-Id: Content-Type: text/plain; charset="us-ascii" To: linux-lvm@sistina.com Jason Tackaberry writes: > > You could either mirror the whole disk using MD *without* persistent > > superblocks > > This sounds like the best and most transparent solution. But > Documentation/md.txt says: > > raid level = -1 linear mode > 0 striped mode > other modes are only supported with persistant super blocks > > So it sounds like this won't work? I'll give it a try and see what > happens anyway. It should work, you only need the persistent superblock, if you want to boot from software RAID. Here the quote from the HOWTO >> 3.7. The Persistent Superblock >> >> Back in ``The Good Old Days'' (TM), the raidtools would read your >> /etc/raidtab file, and then initialize the array. However, this would >> require that the filesystem on which /etc/raidtab resided was mounted. >> This is unfortunate if you want to boot on a RAID. >> >> Also, the old approach led to complications when mounting filesystems >> RAID devices. They could not be put in the /etc/fstab file as usual, >> but would have to be mounted from the init-scripts. >> >> The persistent superblocks solve these problems. When an array is >> initialized with the persistent-superblock option in the /etc/raidtab >> file, a special superblock is written in the beginning of all disks >> participating in the array. This allows the kernel to read the >> configuration of RAID devices directly from the disks involved, >> instead of reading from some configuration file that may not be >> available at all times. >> >> You should however still maintain a consistent /etc/raidtab file, >> since you may need this file for later reconstruction of the array. >> >> The persistent superblock is mandatory if you want auto-detection of >> your RAID devices upon system boot. This is described in the >> Autodetection section. Cheers, Werner