Mirrored disks query

[Jim Wallace]

I have a customer machine (HP-UX 11.11) which has a set of local (data) disks mirrored against a SAN. (The opsys is on locally mirrored disks, by the way).

The customer wants to shutdown the SAN, but we dont really want to shutdown the HP server.

I'm looking at options for keeping the lvols mounted/available but without the mirrors being needed - ie; we'll run run the system just on the local disks.

I'm thinking we could do a vgchange to remove the quorum requirement, and just accept it losing the paths to the SAN disks when that gets shutdown - letting it "sort itself out" when the paths come back later (and resetting the quorum requirement).

Another option of course would be to remove all the mirroring to the SAN and recreate it aafterwards - but this would be very time consuming (there are 20 disks/lvols) and surely cant be the best solution?

Suggestions would be very welcome.

[Torsten.]

Consider to use "pvchange -a n ..." to make the disks unavailable for LVM.
So they are in a clean status.
Once the SAN is available again, activate the LVM access again and sync the disks.

[Jim Wallace]

Thanks for the incredibly quick response Torsten.
Question with this is that with the default being to require quorum, when we deactivate the PV for the SAN disks, would LVM not then prevent continued access to the local disks, or would this only be a problem if any local disk was also unmounted and tried to remount/activate without quorum present?

[Torsten. · Accepted solution]

If the VG is activated, it will stay activated, even if the mirror disks are unavailable.

If you umount and de-activate the VG, you must use the quroum option to activate it again (SAN still down).

vgchange -q n vgxx

But if you "turn off" the disks access for LVM, shutdown your SAN, restart your SAN, activate the LVM access and sync disks, this all should work without problems.

In case of multiple pathes to the SAN you may use "pvchange -a N ...".

[Jim Wallace]

Many thanks (again!) Torsten - I think we'll go with the pvchange you suggest.

[Jim Wallace]

going with the pvchange option.

[Torsten.]

BTW, if the command switch "-a" for pvchange is not available, you need to patch your system.
Patches are PHKL_31216 and PHCO_30698 or their superseding patches for 11.11 (there are newer patches now).

The functionality is called LVM Online Disk Replacement (LVM OLR) - intended for replacing disks.