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Date:      Mon, 26 Jan 2009 22:04:11 -0500
From:      Vladislav Sekulic <vlad.sekulic@utoronto.ca>
To:        freebsd-questions@freebsd.org
Subject:   Adding partitions to gmirror device
Message-ID:  <20090126220411.b9c04ypy0wo04wkk@webmail.utoronto.ca>

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Hi!

I'm running FreeBSD 7.1-RELEASE on a couple of Sun X2100 servers, each =20
with 2X 250GB SATA drives that I've established a gmirror(8) over, =20
following the instructions in section 19.4 of the Handbook.

Now, one of the machines, being transformed into a webserver, needs a =20
separate, newly created /var/www partition (its current partitions =20
only take up 27G of the total ~238G available).

My dilemma is -- how do I add another partition without hosing the =20
system?  It seems to me that there is no other way than to destroy the =20
gmirror, create the new partition, then re-create the gmirror.  The =20
issue is how to proceed in a safe manner, without destroying any data =20
or causing undue hassle (time is of the essence, as always).

My draft plan is as follows, with ad4 and ad6 being the component drives:

   $ sudo gmirror deactivate gm0 /dev/ad6
   $ sudo gmirror deactivate gm0 /dev/ad4
   $ sudo gmirror remove gm0 /dev/ad6
   $ sudo gmirror remove gm0 /dev/ad4

I believe this would result in all metadata associated with the =20
gmirror to be wiped, and hence the gmirror to be destroyed, based on =20
my potentially faulty reading of the manpage.

Then edit fstab to restore the ``/dev/mirror/gm0s1?'' entries to their =20
corresponding ``/dev/ad4s1?'' entries & reboot.

Afterwards, would run ``bsdlabel -e ad4'', then newfs, and finally, =20
redo the gmirror sequence (following the steps in section 19.4 of the =20
handbook, as before).

Am I missing any critical steps here, or have any redundant steps?  Or =20
just not getting it?

Thank you for any pointers!

Vlad

P.S.  Is it possible to operate directly on the gm0 device, i.e., to =20
create a partition using it rather than destroying the entire gmirror?

--
Vladislav Sekulic
Research Computing System Administrator
Systems and Networks Research Group
Dept. of Computer Science, University of Toronto
http://www.cs.toronto.edu/~pocsys




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