Splitting root volume mirrors

[Ian Foster]

Prior to an impending O.S. upgrade on our N class server I'm intending to split the mirror of the root VG off, for regress purposes (already set up by one of my predecessors using MirrorDisk-UX).

I've already got some good info for splitting/mounting/booting and testing from ITRC amongst other sources but I still have one kind of 'grey' area :

I understand the lv's should be split in descending order, with / being last, but I notice in the man page for lvsplit that it says volumes can't be split when activated in shared mode and to use vgchange to make the VG unavailable first.

What does this mean practically in terms of splitting this root volume group ? Single user mode ?

Any clarification on the procedure for the actual split gratefully recieved.

I'm happy with fscking the volumes, modifying fstab and modifying the mirror to be bootable from there.

Many thanks,
Ian.

[Pete Randall · Accepted solution]

Ian,

The note about "shared" mode is referring to the MCServiceGuard environment where it is possible for two servers to have access to the same drives.


Pete

[Stefan Farrelly]

shared mode only applies to a serviceguard environment where a volume group may be accessed by 2 or more servers (if you have a failover).

If youre not running SG ignore it. You can split at any time with no risk. Ive done plenty of these before, and ive never split the mirrors in any particular order or had a problem with it.

[Ian Foster]

Thanks a lot guys. That's all I needed to know.

[Massimo Bianchi]

Hi,
shared mode is intended when in MC/SG configuration, where you can have the vg shared between two or more hosts.

It is absolutely not your case, because vg00 must belong to just one server....


Rememebr another simple procedure, may be you are satisfied wenough the same.


You have disk A and disk B in vg00 , mirrored.

You reduce mirroring and vgreduce vg00, thus removing disk B. disk B is free.


Now, when you install your server, you install it on disk B !


You want the old SYS ? boot from disk A
You want the new SYS ? boot from disk B

I think it's an easier ways. Done it with a customer, that had to test the same application on the same server with 10.20 and 11.00

You have just to pay attention to the HW path, because they are the only incariants between two different OS. Better to extract the disk, if you can.


HTH,
Massimo