IBM RS/6000 - Manual (Page 71)

3.3 Using the Hot-Swap Subsystem
Having the hot-swap subsystem is very useful. As previously mentioned, it allows
you to add, remove or replace disk drives without shutting down and powering-off
your system. There are, however, three levels at which you can use the hot-swap
subsystem.
First, you can use the hot-swap subsystem to simply add and remove disk drives
from the system. You can buy and add new drives with ease, and these can be
quickly configured into your system without affecting the users. You can also
export volume groups and remove the drives to put into other hot-swap systems, or
you could remove a disk from a volume group and use the disk as an extra disk for
another system.
Second, there is replacement usage. You may only have one system with the
hot-swap capability and will only remove drives if they become faulty. In this
scenario, you can replace the drive without powering-off and shutting down the
system. To enable the removal of the drive, the administrator will tell AIX that the
disk is to be removed from the system. If the data on the disk can still be
accessed, the administrator can migrate the contents of the disk to another one or
back up the data on the disk. The disk will then be replaced, and using a backup
of the data on this disk or by migrating the data back, the disk will be re-added to
the system, and any data which was originally on the disk will be restored. In this
scenario, where the data was not migrated, users who were using data on the drive
will be affected. The users will be unable to access their data until a replacement
drive has been fitted and the data restored.
The third usage of the hot-swap subsystem is mirroring, effectively giving the
subsystem RAID 0. Failures happen infrequently, but when the failures do happen,
they can cause havoc with your data. Using mirroring with the hot-swap subsystem
allows the system to carry on using data contained on a disk even if that disk fails
since it will be able to use a mirror. If a disk fails, the disk can be replaced and the
new disk added to the system. A mirror can then be rebuilt without affecting AIX,
the applications or the users. The subject of mirroring is discussed later in this
chapter.
3.3.1 Adding a New Drive to a Live System
When you install a new drive in the hot-swap subsystem, the amber light in the
carrier will flash and then go out. This indicates that the drive has been identified
and is not spinning. At this point, AIX does not know that the drive is present in the
system. To tell AIX that you have added a new drive, you can use SMIT or type:
cfgmgr
from the command line. Running this command will cause AIX to find the drive and
spin it up. You will see the amber light come on at this point and will hear the
sound of the drive spinning up. Using the
lspv command, you will be able to see
your new drive added. f the drive contains a volume group, you access it from your
system by running:
importvg -y VGname hdiskx
Otherwise, you can add the disk to an existing volume group by using extendvg or
create a new volume group by using smit mkvg .
Chapter 3. Hot-Swap Subsystem 47