install with a root mirror

[Chris Howard]

We have a HP-UX 11.11 system with mirrored root drive that we want to do a full install of HP-UX 11.23

I want to keep the mirrored disk out of the new install so that we can reboot back to 11.11 if something goes wrong.

Do I need to explicitly break the mirror before the new install?

[Steven E. Protter]

Shalom,

You should explicitly break the mirror. That is good practice.

Technically, if you do the new OS install and only include the primary boot disk, you will still be able to manually boot the system at console onto the mirror disk.

As a security measure, have an Ignite make_tape_recovery or make_net_recovery backup at the ready.

SEP

[Torsten.]

Shut down, remove the disk, boot with quorum mode and "vgreduce -f" the "missing" disk.

If needed, insert the "old" disk and boot from it again.

[Chris Howard]

Is there some way to do it without physically removing the disk? I'm working remotely.

[R.O.]

You can disable it and prevent LVM from using it:

# pvchange -a N /dev/dsk/cXtXdX

Regards,

[Torsten.]

This is dangerous.

After a reboot, the disk is activated again and will be synced with the other disk.

So your "backup" is gone.




Another idea:

unmirror the drive and clone it with DRD (no unmirror needed, if you have another empty disk).

In case of trouble boot the DRD clone and you are back in business.

[Chris Howard]

I'm going to try this on my test machine:


Build root clone Drive A -> Drive B

pvchange -a N Drive A
reboot and do cold install on Drive A
See if I can boot old Drive B

[Chris Howard]

In my experiment, installing on Disk A works fine.

Booting from Disk B gives me errors about missing Disk A. (The disk is still in place and operational.)

I repeated pvchange -a N (disk A)
but still get the error messages.

As long as it is not actually writing to disk A, I think this outcome will work.

[Torsten.]

pvchange -a N will disable LVM access, but only until next VG activation (e.g. during a boot). Then the disk will be sync again.

So if you do an installation on the remaining disk, after the next boot the installation disk will be synced to your "backup" disk = no backup anymore.

[Elmar P. Kolkman]

After the installation, the PV has been re-created... so the PV-ID is changed and not accepted anymore by the old vg00 of the 11.11 environment.

This means that the data on both disks is still valid and save, but if you will have to boot from the old disk, you need to specify the '-lq' option (low quorum).