Michael Christie wrote:
Hi there all,

I need your help. I have a supermicro server which was running Freebsd 7.1
with 2 SATA drives. I have had G mirror running on the server. I needed to
do a full reinstall of freebsd but was unable to disengage the mirror at the
time. When installing Freebsd, on to the drives i see i have AD4 AD6 and AR0
on the disk label, i have installed the new free bsd in AD4, and the system
would not boot.

I have come across this before where i have to remove AR0 to default the
drive, i can remember reading a thread on how to use “fix it” and using the
live cd. I have google but cannot find it

You do understand that 'ar0' is an ATARAID mirror and nothing to do with gmirror
at all?  gmirror uses device names like /dev/mirror/gm0 typically.

Please is there any one here that can refresh my memory and tell me how to
remove gmirror from my drives so i can do a fresh install,.

You don't need to remove gmirror per-se.  If you do a fresh install on top
of what you have, it will set up the drive you install on as a stand-alone
disk.  In fact, you can take one of a gmirror'd pair and just tweak the device
names in /etc/fstab and run it as a plain disk pretty easily without 
at all.

There will be gmirror metadata blocks on disk, but these wont have any effect
unless you mount partitions on the gmirror device.  To remove those metadata
blocks, just do
 # gmirror clear /dev/mirror/gm0

(or whatever your gmirror device is called) -- obviously *not* while the gmirror
is active.  You may need to allow writes to an active underlying partition by

 # sysctl kern.geom.debugflags=16

The ATARAID mirror you seem to have picked up inadvertently is very similar to
a gmirror RAID in the way it works, except that it won't generally have the nice
behaviour for replacing blown hot-swap drives without having to reboot the 
In any case, you can just ignore /dev/ar0 and mount partitions from /dev/ad4 instead, equivalently as for the gmirror case. To remove ar0, just do:

  # atacontrol delete ar0

Either of these are fairly safe to do while the system is up and running.

Also, I suspect that your system is not booting for a different reason than
you think.  You'ld have to tell us the exact error message you see in order to
get a definitive answer, but given what you've described two pretty likely
problems  are:

   * Early stage boot blocks can't find the kernel image.  In this case
     you'll be dumped at the loader prompt and asked to give the device
     name and path to read the kernel from -- typically something like

     (you can use the 'ls' command in the loader to see what available devices
     there are to try booting from).

   * Can't mount root partition.  Generally this means that /etc/fstab contains
     incorrect data.  In this case, you can probably boot to single user, 
the root partition read-write and then edit /etc/fstab
These are not impossibly difficult things to deal with, but neither are they
entirely trivial, and if you're a beginner and you don't care about what's
currently on the disk, you might find it more productive just to reinstall over
the top of the previous contents.



Dr Matthew J Seaman MA, D.Phil.                   7 Priory Courtyard
                                                 Flat 3
PGP: http://www.infracaninophile.co.uk/pgpkey     Ramsgate
                                                 Kent, CT11 9PW

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