SUMMARY: LSM volrootmir restrictions?

From: Tim Mooney <mooney_at_dogbert.cc.ndsu.NoDak.edu>
Date: Thu, 24 Oct 1996 16:50:11 -0500 (CDT)

All-

I recently asked a question about the restrictions noted in the LSM guide
about mirroring root and swap (the original email is attached after this
message). I was concerned that the LSM guide seemed to be implying that one
could not use the rest of the disk that was being used as a mirror in the
special case of mirroring / and swap1.

I received email from:

        alan_at_nabeth.cxo.dec.com
        Andrew Weston <andreww_at_adacel.com.au>
        Martyn Johnson <Martyn.Johnson_at_cl.cam.ac.uk>
        Steve Thompson <smt_at_NICS1.CORNING.COM>
        chandrasek_at_odixie.ENET.dec.com

My thanks to each of them!

Martyn's response said it best, so here it is:

        My interpretation of the restriction was that no partitions of
        the target disc should be in use at the time you do the volrootmir
        operation. I have certainly had no difficulty in using the
        remaining space as general purpose space afterwards. In my case the
        original root disc was a 1Gb disc and its mirror was a 9Gb disc, so
        obviously it would have been a showstopper if I couldn't use the
        surplus space on the mirror disc.


Since receiving the replies, I've gone through the root mirroring procedure
as documented in the LSM guide and have successfully mirrored rz0a
(root_domain#root) and rz0b (swap1) to rz2. rz0d (the remainder of rz0)
and rz2d (the remainder of rz2) are being used as (non-mirrored) LSM volumes.

Thanks to everyone for the responses!

Tim

-- 
Tim Mooney                              mooney_at_toons.cc.ndsu.NoDak.edu
Information Technology Services         (701) 231-1076 (Voice)
Room 242-J1, IACC Bldg.                 (701) 231-8541 (FAX)
North Dakota State University, Fargo, ND 58105
--My original question--:
All-
I'm investigating setting up LSM mirrors of /, swap1, and /usr on our backup
server to ensure high-availability of that machine.  The machine is running
Digital Unix 3.2g, and all current filesystems are AdvFS, including the root
filesystem.  I've used LSM & AdvFS for a while and am familiar with most of
the features of each, but I've never used any of LSM's mirroring capabilities.
My question is with regard to the restriction that "No partitions on the
mirrored disk can be in use" (page 4-3 of the Logical Storage Manager guide).
This would seem to indicate that if I use root & swap1 mirroring I cannot
use any of the rest of the disk on which root & swap1 are being mirrored to
(i.e. if rz0a is root_domain#root and rz0b is swap1 and I want to mirror
them to rz4, does that mean that rz4 can't be used for anything else?).
Is this correct, or am I misinterpreting what the restrictions really are?
The machine in question has 4 rz28m disks, two of which are currently 
completely unallocated.  root_domain#root and swap1 together account
for about 1/4 of rz0.  If the restriction is that the disk containing the
mirror of root and swap cannot contain anything else then I'm either going to
have to "throw away" 3/4 of the space of an rz28m or get a smaller disk to
contain the mirrors of root and swap1.
I will summarize.
Tim

Received on Fri Oct 25 1996 - 00:12:37 NZDT