HP-UX vPars and Integrity VM V6.3 Administrator Guide

6.1.5 Storage configurability
VSP administrators expect the vPars and VM guests to be as easily configurable as HP Integrity
servers. The vPar and VM guest storage subsystem allows for easy changes to the storage devices
through vPars and Integrity VM commands. Using these commands, the VSP administrator
dynamically adds, deletes, and modifies storage devices on VMs and vPars. Guest administrators
can change some storage, limited in scope by the VSP administrator, using the virtual console.
6.2 Storage architectures
The vPars and Integrity VM guest storage subsystem provides three types of storage architectures:
• Shared I/O
• Attached I/O
• NPIV
6.2.1 Shared I/O
The shared I/O architecture is a means by which a vPar and VM guest accesses an entirely
virtualized storage subsystem provided by the VSP. The VSP emulates a HPVM proprietary hardware
device to the vPar or VM guest. The vPar or VM guest storage subsystem interacts with the VSP to
complete I/O operations to the VSP storage entity. This abstraction enables the VSP administrator
to share physical VSP storage hardware across multiple vPars or VMs and to allocate that storage
at sub-LUN levels.
The individual storage LUNs are shared by dividing a VSP LUN into smaller parts such as logical
volumes or files. Each of these sub-LUN VSP entities can then be used as media for separate virtual
storage devices. The vPars and VM guests access the virtual storage devices as real storage devices,
with no knowledge that the virtual storage media is actually a sub-LUN VSP entity.
The way the virtual storage media is accessed by the vPar or VM guest storage subsystem allows
them to share physical VSP storage adapters. All virtual storage media is accessed through
user-defined interfaces on the VSP. The VSP maintains complete control of the physical hardware
and handles the vPar or VM guest I/O operations just as it would be handled for any other user
application. Thus, just as hardware is shared among normal applications running on the VSP, vPar
and VM guest I/O is shared across the physical storage as well.
The shared I/O architecture also provides for whole LUNs to be virtualized. While this does not
increase storage utilization, it does provide higher storage availability. Because the LUN is
virtualized, the guest OS need not support the physical VSP LUN. It is sufficient to support the
virtualized version of VSP LUN. Thus, by using shared I/O a vPar or VM guest can run with any
physical hardware that is supported by the VSP.
Finally, all vPar or VM guest I/O requests in shared I/O are processed by virtual adapters. A
virtual adapter is an emulation of a proprietary adapter type that a special driver in the guest OS
accesses. The virtual adapter uses internal vPar or VM guest storage subsystem calls to handle
communication of vPar or VM guest I/O to the virtual devices. This connection between the virtual
adapter and the virtual devices must not resemble anything in an HP Integrity server system. It is
emulated so that the vPar or VM guest does not know the difference.
6.2.2 Attached I/O
Attached I/O allows a vPar or VM guest visibility to the real device and its properties. In this
architecture, the vPar or VM guest storage subsystem attaches a LUN path on the VSP to a virtualized
storage adapter. The LUN can be a DVD, tape, or media changer.
The main difference between shared I/O and attached I/O is the degree to which a physical
storage subsystem is virtualized. In shared I/O, an entire storage subsystem is virtualized. Therefore,
all physical adapters on the VSP and all the storage connected to those adapters can be shared
64 Storage devices