Break the root mirror

[Amy Ng_2]

We have the root drive mirrored on all our HPUX servers with the lvextend command. We are planning to do a ServiceGuard upgrade on our cluster systems. We have HPUX 11i installed on these servers. Is there anyway that I can break the mirror without physically
removing the alternate root drive? If the upgrade is unsuccessful, I want to be able to boot from the alternate drive.
Thanks,
Amy

[A. Clay Stephenson]

No, and in fact removing the PV is the safest way because it prevents you from accidently harming the data. However, a still better way is to create a lifeboat disk by dd'ing your current boot disk onto another disk and leaving your mirroring intact. Bear in mind that an MC/SG upgrade should not be a big deal because you have moved your packages to another node so that even if you blow this node to pieces, you haven't actually hurt anything.

[Alzhy]

Amy,

Peace.

What I usually do is simply use dd.I break of the mirror disk from the VG completely and:

dd if=/dev/rdsk/c0t6d0 of=/dev/rdsk/c1t6d0 bs=4096k

A 36GB SCSI OS disk is usually done in under 45 minutes.

Others will probably espouse Ignite to tape or network - but...

[Prashant Zanwar_4]

Have a ignite, lvreduce root mirror, physically take disk out of server half way.. and go ahead for patching..

lvreduce -m 0 /dev/vg00/lv...

just reducing mirror to 0 also should be ok..



Rgds
Prashant

[Mark Greene_1]

Before you do anything, be certain that both sets of drives are set to boot:

lvlnboot -v

and then run this for both boot disks:

lifcp /dev/rdsk/cxtxdx:AUTO -

and be sure it returns:

hpux -lq

Then you'll know both drives are bootable before assuming anything incorrectly.

mark

[Sanjay_6]

Hi Amy,

Are you looking for doc on how to boot from a split mirror, then check this one out from ITRC,

http://www2.itrc.hp.com/service/cki/docDisplay.do?docLocale=en_US&docId=200000063238284

The ITRC doc id is X1401978.

The procedure was good for 10.20 and it is good for 11i.

Hope this helps.

regds

[Jeff Gyurko]

I'm interested in why Clay states you can't. We split the mirrors for patching here which sound like a similar procedure. We recently had a situation with a patch install that required us to boot off the alternate disk. Sure we had to modify fstab and the lvlnboot information to stabilize, but it worked just fine.

[A. Clay Stephenson]

Rather than saying you can't I really meant you shouldn't. Removing the alternate boot disk means that you have a known good boot disk that requires no intervention (other than "boot alt") if you have set -lq in the boot string of both the primary and alternate boot disks. Also, removing the alternate disk means that you can't possibly destroy the data on it by accident.

In my case, I always leave them mirrored but I have lifeboat disk(s) ready to simply move to the boot slot(s) so that I know I can always get back to my pre-patched condition.