AIX 5L Problem Determination - IBM Redbooks

This example shows that the volume group testvg with a current 9.1 GB disk has
a maximum number of 1016 PPs per physical volume. Adding a larger 18.2 GB
disk would not be possible; the maximum size of the disk is limited to 17 GB
unless the maximum number of PPs is increased. Using the chvg command to
increase the maximum number of PPs by a factor of 2 to 2032 PPs allows the
volume group to be extended with physical volumes of up to approximately 34
GB.
7.3 Disk replacement
7.3.1 Replacing a disk
AIX, like all operating systems, can be problematic when you have to change a
disk. AIX provides the ability to prepare the system for the change using the
LVM. You can then perform the disk replacement and then use the LVM to
restore the system back to how it was before the disk was changed. This process
manipulates not only the data on the disk itself, but is also a way of keeping the
Object Data Manager (ODM) intact.
The ODM within AIX is a database that holds device configuration details and
AIX configuration details. The function of the ODM is to store the information
between reboots, and also provide rapid access to system data, eliminating the
need for AIX commands to interrogate components for configuration information.
Since this database holds so much vital information regarding the configuration
of a machine, any changes made to the machine, such as the changing of a
defective disk, need to be done in such a way as to preserve the integrity of the
database.
The following scenario shows a system that has a hardware error on a physical
volume. However, since the system uses a mirrored environment, which has
multiple copies of the logical volume, it is possible to replace the disk while the
system is active. The disk hardware in this scenario are hot-swappable SCSI
disks, which permit the replacement of a disk in a production environment.
One important factor is detecting the disk error. Normally, mail is sent to the
system administrator (root account) from the Automatic Error Log Analysis
(diagela). Figure 7-1 on page 145 shows the information in such a diagnostics
mail.
144 IBM ^ Certification Study Guide - AIX 5L Problem Determination Tools and Techniques