Presenting LUNs to VM Host for VM Guests

[N Ward]

We have a several LUNs presented to a VM Host for the VM Guests and want the guests to have more space.

Is it best to expand the single LUNs or present new LUNs which in turn will be presented to the VM Guests? I would guess the easiest is the first method.

My questions is, how does the VM Guest pick up the extra space that it now has?

[Torsten.]

This really depends on how the guest handles disks (what OS?).

[N Ward]

HPUX 11.23 on VM Host and VM Guests and Integrity 3.5 on 4 Guests and 2.0 on 2 others.

[Torsten.]

You have the choice - increase the disk size and use vgmodify on the guest or add a new disk to the LVM configuration.

[N Ward]

If a new LUN is presented to the VM Host, it requires presenting to the VM Guest manually. However if the existing SAN LUN is expanded the VM Guest can pick this up with vgmodify?

[melvyn burnard · Accepted solution]

If your VM Host is running HP-UX 11.23, you will need a reboot for it to pick up any extending done to LUN's presented to it.
It may just be easier to present new LUN's unless you can afford the downtime of a reboot.

[N Ward]

Thanks Melvyn (we have met before in Bristol), I was lead to believe that vgmodify would work to pick up the new space, without a reboot?

I haven't looked at this command in great detail just yet, but it appears to be able to increase the number of extents available following dynamic LUN size increases.

I believe it depends on the version of the Volume Group too. Version 2.0 is supported now, but version 1.0 only from Sept 2008 versions of HPUX 11.23.

[melvyn burnard]

to my knowledge, DOLE (Dynamic Online Lun Expansion) is only available on HP-UX 11.31.
With 11iv2 a reboot is still required to "read" the expansion on the LUN, but I will check.

[N Ward]

Much appreciated Melvyn, if thats the case, your suggestion of merely adding new LUNs will be our best approach as below.

The extra LUNs get presented to the VM Host I then present them to the VM Guest and no reboot for the Guest is required? Just an ioscan and insf -e?

[Kapil Jha]

Yes if it is 11.23 you will need to have a reboot for OS to recognise new LUN size.

Its better if you can add a new LUN unless you already you have lots of LUNs and want minimum LUNs to manager.

BR,
Kapil+