hmm, your name suggests you know VMS too, LOL.

There is no direct answer to this because it will depend on so many details of your setup (which you didn't describe in detail so far). I will try to give you an overview and you may want to ask details as we go along.

It is possible to put physical disks into POWER-systems and use these, but this is commonly only done for VIOS systems. All the other LPARs get disks usually from some external (SAN) storage. I will describe this here.

There are two common ways to attach external disks to an LPAR: vSCSI and NPIV. Both involve the VIOS and the most common setup is to use both: vSCSI for the boot disks (that is: rootvgs) of the LPARs and NPIV for the data/application disks.

vSCSI is the simplest method: first, on the VIOS a virtual SCSI adapter is created and then attached to the LPAR. Now it is possible to create virtual SCSI disks from SAN disks attached to the VIOS and attach these virtual SCSI disks to a certain LPAR/certain adapter. When the LPAR boots it sees this virtual disk as a SCSI-disk attached to a SCSI-adapter.

The advantage of doing it this way is that you can do everything you do with a real SCSI disk, including booting from it, from the LPAR. Still, because the gear the LPAR uses is in fact virtualised, you can still use LPM (Live Partition Mobility). The VIOS of the source- and target-machines (="Managed System") will move the virtualised adapters and disks around so that on the target-MS you have the LPAR running the same way you had it on the source-MS. On the downside the VIOS is involved a lot relatively in the handling and utilisation of the vSCSI disks and when you have much traffic on vSCSI-disks the VIOS needs an increasing amount of (processor and memory) resources.

This is why disks you do not need to boot from ("data disks") are commonly not vSCSI but NPIV: the VIOS only creates a virtual FC-adapter (the VIOS gets the physical FC-adapter attached) and exports that to the LPAR, which in turn uses it to connect to SAN LUNs directly. The LPAR needs to use the respective FC-driver (multipath for IBM storage, powermt for EMC, ...) to access the LUNs. The zoning gets a bit more complicated too, because the LUNs need to be zoned to the LPAR now. On the upside the VIOS is less involved and some limitations of SCSI do not apply.

There are a few redbooks from IBM about their virtualisation techniques which i suggest you download and read.

I hope this helps.

bakunin