How do I backup a multi-disk volume group? From: (Daniel Packman)

[ Ed.: I have not verified this procedure. I would actually recommend
NOT to have one volume group span multiple disks unless you really
need such big logical volumes. ]

1. If you have a set of three or more disks in a volume group
(typically 3 for 5xx machines with three internal drives;
with only two, the procedures outlined here have to be modified
to ignore the fact that you don't have a quorum in the volume group)

2. If one drive has failed (usually only one fails at a time :-) )

It is possible to go through a service boot (the volume group is called
rootvg and one of the 2 good disks on it is called hdisk0):

importvg -y rootvg hdisk0
varyonvg -f -n -m1 rootvg

These commands will work, but give error messages. If you wish to mount
a user filesystem, say /u on logical volume /dev/lv00, then

mount -f /dev/lv00 /v

will work only if jfslog, the journaled file system log device, is not
on the damaged disk. If it is, you must (and can in any case) mount the
filesystem read-only:

mount -f -r /dev/lv00 /v

This crucial and rather obvious point baffled several level 3 support
personnel at Austin as well as myself for almost a week. Once the file
system(s) of interest are available, they can be saved to tape for
restoration later. Of course, one can expect only about two thirds of a
filesystem to be recoverable if it spans all 3 physical disks. One
other point to remember is that the standard boot procedure from floppy
includes the restore command but does not include the backup command.

* If you do not have other RS6000 machines at your site it is imperative *
* that you either build a bootable tape which includes either restore or *
* tar or cpio (a bootable floppy set will not have enough space) or at the *
* very least copy onto a spare floppy backup, cpio, or tar. The floppy *
* should be created with backup -ivq so that its contents can be read into *
* the memory resident system after booting. *

All is not lost if tar, cpio or backup are available on an undamaged
disk that can be mounted. Since tar and cpio are in /bin, they may both
very well be unavailable.

It is a very good idea for those who have tape devices to build a
bootable tape with their desired extra commands in it. Follow the
instructions from IBM but add your desired commands to the following
three files:


If you have anything other than a minimum memory configuration, you
should be able to add many commands.
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