To PVG or not to PVG

[Matthew Murdock]

In our 2 Node HA Service Guard configuration, we usually sell 2 Arrays (3Par P7200C now), for High Availability for our Oracle RAC installation. This presents a problem of sorts. This is on a 11.31 March 2014 HA-OE distro with the latest OS patchset installed.

I create a vg (300gb) for shared mode between the 2 nodes using one of the Vdisks/Luns from the first array. No problem works like a champ.

However, to accomodate the 2nd Array/Lun (300gb), I have to add the PV (lun) into the existing vg with vgextend. I understand that.

This then makes the VG twice the size (600gb) available for LV's to be created on

(I know the steps on creating and importing and activating in Clustered Shared mode).

1) I create the LV (strict/Contigous is set during LV Creation) of the example  size of 200gb, does HP/UX LVM gurantee that the LV is created on the first 300gb PV or will it position the LV across both disks?

If it puts it across both PV's and one of the PV's dies, I loose the LV/Data. It is a RAC ASM Controlled disk.

However, if it does not spread the LV across both PV's, I then mirror the LV to the second PV with lvextend.

2) Can I set the -lq option on a shared clustered VG, as it is done with mirroring a boot disk (im not MIRRORING THE BOOT DISK) to ignore quorum in the event of a mirrord PV fails? If so how would I do that with the shared VG/LV/PV?

3) It may be simplier and just as HA to use one Array, one Lun  rather than 2 array's and 2 Luns?

[Torsten.]

1) You can use PVG, but if you have a single LUN per array in the VG you don't need it. Just specify a single disk device during lvcreate and the other disk during lvextend. The "strict" will ensure what you want to do.

2) why not? Set -lq. It comes into play if you boot the server and activate the volume group.

3) more redundancy is always better ...