I recently was involved in troubleshooting a problem on a HPUX system.It turned out that the system command iostat showed one disk and the configuration (/etc/lvmtab) showed another disk. Yet another symptom was that lvdisplay didn't work at all. Since there had been a bunch of activity on that system it took some detective work to find out that the reason for the problem was that the raid controller had been replaced.

So this still amazes me. The configuration said one thing and the monitoring tools another but still the host worked just fine. Actually it was a little slow but apparently the mix-up of disk devices didn't matter. So when other systems have their hardware changed you need to rescan it so how do you do that on HPUX? Well this is how you fix your disk configuration if you have one volume group named "vg00":

In multiuser mode:
#/sbin/vgexport -m /vg00.map -s -p -v vg00
 
Reboot the system and go to maintenance mode:
#shutdown -ry 0 [Esc]

Main Menu: boot pri isl
Interact with the IPL?> y
ISL> hpux –lm

 
#/sbin/vgexport -v vg00
#/sbin/mkdir /dev/vg00

 
Create the special device file (SDF), use the next available minor number:
#/sbin/mknod /dev/vg00/group c 64 0x##0000
#/sbin/vgimport -m /vg00.map -N -v -s vg00 vgchange -a y vg00

 
Reboot the system to multiuser mode again.

Preemptive comment response: No I don't know why the system was not reconfigured immediately after replacing the RAID controller. Probably because everything seamed to work after booting.