To use a mirrored disk of vg00 to boot a other box - lvsplit or pull out?

[stephen peng]

Guys,

I've got a box with its single root disk failed, and there was a-same-type box, with vg00 mirrored, so I plan to make use of this configuration. I could directly pull out one of the mirrored disks and make it boot disk of the failed box, but I also want to know whether I could use lvsplit to accomplish this job. 

Anyone offer me some explainations?

regards

Stephen

[Ralf Seefeldt]

Hi stephan,

you could use vgsplit.

As I assume, you have a replacement disk on hands, you simply could execute sync (several times) and pull the mirror.

Next, I would recreate the mirror with the sparedisk. Thus, you know, the mirroring works as expected.

If the mirrored server is fine again, boot the broken server from the original mirrordisk.

Bye

Ralf

[stephen peng]

Ralf,
Thank you for you reply.
1, Is there a command named vgsplit?
2, Is that safe to "pull the mirror"? maybe I tried this serveral times, but all in situations that the mirrors were failed.

regards
Stephen

[Dennis Handly]

>1, Is there a command named vgsplit?

Only 11.31, see:

http://h30499.www3.hp.com/t5/System-Administration/VGSPLIT-in-HP-UX/td-p/5076793

[chris huys_4]

Hi stephen,

Looks to me like a bad idea. Well actuall 2 bad ideas. 

1. the lvsplit bad idea.

You have a system A, where vg00 consists out 1 bootdisk and the bootdisk is failed.

And you have a system B,  where vg00 consists of 2 bootdisks and the bootdisks are mirrored , and both bootdisks are still good.

And now you want to use 1 of the 2 good bootdisks of system B, via "lvsplit", to boot system A.

1.a lvsplit might be good for data lvm volumegroups, but for vg00 , you might think twice before you get a procedure that will work when the bootdisk that is left over after the lvsplilt gets bad and you need the lvsplit'd disk to save the day. I got it working 10 years ago on hp-ux 10.20, but on hp-ux 11.x i didnt get it working afai can remember.

1.b why would you lvsplit ? You are not gonna be able to use it for the system B anyway anymore, once you use it to boot system A.

1.c. a lvsplit'd bootdisk of system B; would, suppose system A can boot from it, what I highly doubt, cause system A to have the same hostname/ipaddress as system B. I dont think neither system A or system B will like that.

2. bad idea 2 : the using of a bootdisk of system B to boot system A.

see 1.c above.

3. So a better plan would be. (and a plan that would propel you in the years 2010 ;) )

3.a. take a ignite backup B1 of good system B.

3.b lvreduce/vgreduce the mirrorbootdisk from  system B.

3.c take a new ignite backup B2 of good system B.

3.d insert the reduced (and now empty) mirrorbootdisk in system A.

3.e use the ignite backup B2 of good system B, to reinstall system A, on the before mirrorbootdisk of system B, all the while changing the hostname/ipaddress /etc.. to reflect system A.

Oh yes, and use make_net_recovery and thus a ignite server, for the ignite backups.

Best Regards,

Chris

[Chirag Parikh]

Hi,

I think, you may do lvreduce and vgreduce on the server where both the disks are working for secondary disk. Remove secondary disk after that and plug that into other server where single boot disk failed. But make sure while booting that system, you need to stop the booting sequence and change the system parameter like IP configuration / Hostname / Kernal parameter if any....otherwise it will conflict with the other server after coming up on network.

Hope that i have cover all the concerns.

Thanks & Regards,

Chirag Parikh.

[stephen peng]

Chris,
Thank you for your detailed reply and sorry for my late kudos.
There was no ignite server so ignite backup was not my option.

regards
stephen