Handbook RAID1 example

[Daniel Gerzo]

On Wed, 25 Jan 2012 11:16:25 +0900 (JST), Hiroki Sato wrote:
> wb> Then add a note or warning along the lines of "The procedure 
> shown can
> wb> only be used if the last block of the drive has not been already
> wb> allocated to a partition.  If the last block has been included in 
> a
> wb> partition, back up, repartion leaving at least one unused block 
> at the
> wb> end of the drive, create the mirror, and restore."
>
>  I think we should rewrite this section not to create a malformed
>  partition table by configuring gmirror in some way.  If all of
>  partitions are UFS, the following procedure should be safe:
>
>   1. gmirror label gm0 /dev/da1, and edit /boot/loader.conf to load
>      the kernel module.
>
>   2. Reboot and check if gm0 is recognized even after that (just in
>      case).
>
>   3. Create partitions in /dev/mirror/gm0 based on ones in /dev/da0.
>      If capacity of /dev/da0 and /dev/da1 is the same as each other
>      gm0 should be slightly smaller by the last sector.
>
>   4. Dump & restore each partition from /dev/da0* to 
> /dev/mirror/gm0*.
>      Install a boot block if necessary.
>
>   5. mount /dev/mirror/gm0s1a /mnt, and edit /mnt/etc/fstab to mount
>      gm0.  Also, apply the same change to /etc/fstab in /dev/da0.
>
>   6. Reboot and check if gm0 is mounted as the root partition.
>
>   7. gmirror add gm0 /dev/da0, and wait for the rebuild.
>
>  The primary difference between the above and one in the handbook is
>  to use /dev/da1 for gm0 first.  By doing this, both making a backup
>  of /dev/da0 and repartitioning before setting up the mirror
>  configuration can be done virtually.  The step 3 may be complex in
>  some cases, but I personally think partitioning /dev/mirror/gm0 by
>  gpart based on the existing /dev/da0 is not so difficult.

Basing on my previous discussion with pjd@ I believe that this is the 
correct way of setting up gmirror. Pawel, could you confirm please?

-- 
Kind regards
   Daniel