OK. I think what you need is to first understand how virtualisation in general and virtualisation the IBM way in particular works. Only then we can care to certain specifics. Lets start:

Take a look at your PC: you have a mainboard inside, onto which a SCSI-Adapter is attached. To this SCSI-Adapter is a disk (or several of them, maybe other devices like CD-ROM drives, etc.) attached. Further, there is some amount of memory and one or more processors.

Let us suppose for a moment that we want to virtualise this system so that we run several logical systems off this hardware. We could divide the memory up between the logical systems and we could also divide the processors between these systems. It would be even possible to makde these shares dynamic so that we take away reosurces from a system which doesn't need it at the time and give it to another which does, then reverse the process as the loads change.

This works well, because processors and memory are "anonymous" resources. They have no content of their own and can therefore be easily attached and reattached to a system. This is not the case with disks, because disks have a certain content. You cannot add "more disk" or take away "some disk" like you could add or remove some GB of memory. This is why virtualisation needs to treat disks differently than other resources.

For this, storage devices were invented. You no longer have physical disks locally installed in your computer (which is already virtualised) but you have a specialised system - the "storage" - which is basically a lot of disks with some logic on top to create virtualised disks of arbitrary size and attach them to some external systems. Examples for such storage boxes are the DS8000 from IBM, the VMax from EMC (these are both the enterprise-level systems), the IBM V7000 and EMCs VNX (the respective midrange category) and similar systems.

In most cases you have several hardware boxes, each with several virtualised systems needing disks and one or more storage boxes providing these disks. To organize all this it is common not to attach the storage directly to such a system but to connect all involved parties to a common network connected via specialised switches and utilizing special broadband communication pathes - the "Storage Area Network" or "SAN". SANs usually run on fibre optic cables and use FC (Fibre Channel) communication. Like Cisco is industry-standard for network switches Brocade is industry-standard for FC switches.

Note that this network of disks connecting to their respective hosts needs to be a lot more reliable than a normal network: in a normal network if a packet is lost it is simply retransmitted - IP has a lot of error-checking and -correcting built in. When a packet in a SAN is lost it results in a disk read/write error. This is why communication pathes are usually redundant, with two or even more parallel connections just in case. This is why the whole system is often called a "fabric" rather than a "network".

Further, with so many logical disks (sometimes thousands of them) and systems involved there needs to be some sort of security so that each host only sees the disks it is supposed to use: this is usually done on the switches of the SAN network and the process is called "zoning". A "zone" basically states that only adapter X is allowed to see disk Y. Because adapter X is a virtual adapter attached to system Z only this system can see the disk. The identification works by a system similar to the MAC-addresses of a network: WWNNs (World Wide Node Name) and WWPNs (World Wide Port Name). Read the Wikipedia article about FC for more details.

So, basically, to get a disk to your system: you need to create one on the storage box, get it zoned to your system, then start using it. I know, this, while this is true, it is like explaining how to fly a plane by "get into the plane, take a seat in the pilots seat and start flying" - way too general. It was the best i could come up right now, though. You need to understand some vital basics before you can even ask the right questions.

I hope this helps.

bakunin