Unmirror vg00 to patch

[EU-Admins-UNIX]

Hi

Would it be advisable to unmirror the root VG before applying patch bundles?  If so, how does one achieve this in the most efficient way?  does lvreduce -m 0 give the same result as lvsplit?

One thing I plan to do before all this is to attempt to boot from the mirror, as this has not been done on this server yet due to storage allocation issues.

Regards

Tariq

[Torsten.]

lvreduce -m 0

will delete the mirror - this is NOT what you want to do.


What OS is running?

With 11.23 and 11.31 you can create a clone of the OS using DRD, patch the clone and finally boot the clone. If anything goes wrong, just boot the original again.

or vice versa

create the clone (just in case), then patch and boot the original, you have the clone as fallback.

http://www.hp.com/go/drd

[EU-Admins-UNIX]

Torsten

We are running 11i v3

Cloning is new to me.  What are the steps?

If lvreduce -m 0 deletes the mirror, it wil still be a bootable device, no?  What I planned to do was to patch the mirror (alternative), if this failed for whatever reason, I would've booted the primary, and re-mirrored onto the alternative?

Have I got this wrong?

Regards

Tariq

[Torsten.]

lvreduce will remove the LVM layout - consider this as data lost.

I added a link into the previous post:

http://www.hp.com/go/drd

[Ken Grabowski]

Torsten is correct, drd is closer to what you say you want to do.  lvreduce is data lost. 

You may also roll back software patch installations. SD-UX provides a process that keeps prior patches on the system until you clean them up, and allows you to roll back to them.

I would also suggest you use ignite's make_net_recovery utility to make a bootable image of your vg00 base operating system prior to patching or major software changes. Under a worst case scenario, you can reinstall on the same system, or another similar system.

[EU-Admins-UNIX]

I didn't realise lvreduce meant data lost.  I thought that once the mirroring was broken, you'd still have a copy of the root/boot disk on the mirror.

Before DRD was available, how was this process carried out, as I dont have capacity for creating a 3rd clone disk?

Regards

Tariq

[Torsten.]

The old fashioned way is to do an ignite backup and restore this if needed.

Consider to remove the mirror, use the second disk as a drd target. If everything is ok, mirror again.

[Ken Grabowski · Accepted solution]

lvsplit does something like what your thinking about. Combined with lvmerge it allows the splitting of a mirrored logical volume into two logical volumes, and the later merging back to one.  For those who have a boot from SAN configuration they can usually make a snapshot, BCV, or mirror split at the array level. 

If you have 11iv3 March 2010 or later installed, there is now a snapshot feature that might help you. I have not used it, so I can't comment on its good or bad sides. I suggest you review the LVM Admin guide for 11iv3.

LVM Admin Guide

Without SAN boot, DRD, or Snapshot, and often even with those capabilities, the standard procedure usually involves a make_net_recovery or make_tape_recovery image of vg00 followed by a full system backup. Then apply the patch bundles. If possible, have application teams test any critical applications on the host after the patching is complete.

Normally you start with the least critical systems like development or test, and let the newly patched system(s) run for a few days or weeks. If no apparent problems have occurred, then you apply to the next level of systems and repeat until you have worked your way through the production environment(s).

If you are applying a major bundle of patches the likelihood is any problem encountered will be with one or two patches, not all of the bundle.  You would deal with them as the problems arise. Either roll back that patch or apply a new fix if one is available.

Once you have done patching for a while, you will learn that you usually take a conservative approach to patching and only apply new patch releases to fix an actual existing problem. Patches are rated on HP's level of confidence and the age of the patch. I recommend that you only apply patches that are proven when possible.