Extending a Virtual LvDisk online

[Hugo F Martinez]

Hi folks,

Im trying to extend a virtual disk on a VM, this are the steps I've done so far,

On host
lvextend -L size /dev/vgvmtest/lvtest3_vg01

On virtual guest
ioscan -fnNC disk
diskinfo /dev/rdisk/disk7

And I could not see the new size of the disk, so I could not vgmodify the guest vg

Any hint?

[Eric SAUBIGNAC]

Bonjour Hugo,

Two things :

1) Limitation of HP-UX

Which version of HP-UX is running inside the guest ?

If it is not HP-UX 11.31 and whatever the harware is, virtual or not, increasing the size of a disk is not acknowledged by HP-UX if the disk is in use.

As I understand your configuration the virtual disk is used by the VM Guest with LVM. If the corresponding VG is activated in the guest, you will see no difference with diskinfo until the VG is deactivated.

2) Limitation of HPVM

Regardless of the first point, increasing the capacity of a backing store (raw device, LV device, or file device) must be propagated to the VM Guest OS by HPVM. I don't remember exactly, but I think it has began to work well only whith HPVM 4.1

In a summary to have online disk expansion working well : Host 11.31, Guest 11.31 and HPVM >= 4.1

And of course better to work with LVM 2.x and OnlineJFS to take advantage of disk expansion. But it is an other story.

Regards

Eric

[Hugo F Martinez]

Im using HP-UX 11v3 with HPVM v4.2. And the version of the vg on the guest is 1.0.

One thing I should be able to extend the vg online with vgmodify -a -E . But I need first to see the new size of the Virtual LvDisk on the guest, which is my problem

Regards

[Eric SAUBIGNAC]

"And the version of the vg on the guest is 1.0.One thing I should be able to extend the vg online with vgmodify -a -E . "

NO. You won't be able to extend the VG online with LVM 1.0. As far as I know it is possible to do it online only from LVM 2.0 version. With LVM 1.0, you can extend the size only when the VG is deactivated and of course if max PE/PV is high enough to support the new size.

"Im using HP-UX 11v3 with HPVM v4.2"

Yes, but what about HP-UX in the VM Guest ? If it is also HP-UX 11.31, I am a bit surprised that you can't see the new size with diskinfo.

Eric

[Eric SAUBIGNAC]

Oups, totally forgot : vio or avio drivers ?

[Hugo F Martinez]

Im suprised too, the guest OS is also 11v3 and Im using just vio. Cant upgrade to avio on this one because of a limitation on the iSCSI

[Eric SAUBIGNAC]

VIO : here is the heart of the problem.

An extract from AVIO guide february 2011 :

--------------------
AVIO supports online expansion of backing store capacity. 11iv3 AVIO guest dynamically detectsbacking store capacity increase and makes the additional space available in the guest.
--------------------

Did not found that VIO doesn't support it, but I guess it don't.

The problem is that LV on iSCSI as LV AVIO backing store is not supported. RN HPVM 4.2.5 January 2011 :

--------------------
iSCSI-based backing stores are not supported with a physical volume under a logical volume that is then exposed to guests as a virtual disk using AVIO.
--------------------

So ... I see no solution to do it on line. You will have to stop the VM :-(

Is it possible that you modify the design ? For example, if you use raw iSCSI backing store instead of LV iSCSI backing store you you should be able to use AVIO drivers ?