HP vPars and Integrity Virtual Machines V6.1 Administrator Guide

9.1.2.2 Attached I/O
Attached I/O allows a vPar/VM to access to a VSP LUN directly. In this architecture, the vPar/VM
storage subsystem attaches a LUN on the VSP to a virtualized storage adapter. A LUN can be a
disk, DVD, tape, media changer, or other peripheral device types. Because attached I/O does
not require device virtualization, the performance of attached I/O might be better than shared
I/O.
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 may be shared
among vPars/VMs. In attached I/O, only the storage adapter is virtualized. Therefore, only the
VSP physical storage adapters may be shared. At least one LUN, the attached LUN, cannot be
shared. It is owned and solely controlled by the vPar/VM to which it is attached.
To provide the vPar/VM with complete control over attached devices, the vPar/VM storage
subsystem interprets I/O requests from the guest device drivers into I/O requests that can be
completed by the VSP storage subsystem on the vPar/VM's behalf. In the process, the VSP storage
subsystem sends all the actual data and responses back the vPar/VM device drivers. With all this
data, the vPar/VM device driver is in complete control over the device. As such, the guest OS must
have built-in support for the attached VSP LUN to use it.
Attached I/O uses a virtual adapter to communicate with the guest OS and the attached LUN. The
virtual adapter either can be an emulation of a real adapter or it can be controlled by a special
driver loaded into the guest OS. Either solution produces a virtual adapter that communicates with
both virtual devices and attached physical devices.
9.1.3 Attached device support in AVIO
AVIO storage supports attached devices (tapes, changers and burners) on HP-UX 11i v2 and HP-UX
11i v3 guests. Attached devices configured using AVIO (avio_stor adapter)::
• Allow sharing of tapes, changers, and burners among multiple guests and host
• Support of USB 2.0 DVD burners
• Improved performance
AVIO (avio_stor adapter type) supports USB 2.0 DVD burners.
To identify USB CD/DVD devices, use the ioscan -fun command.
NOTE: Because vPars/VM might do four to six calls to open() on a DVD when accessing it,
and hpvmcreate or hpvmmodify command might take more than a minute to complete when
there is no media in the drive. Example commands that could appear to hang are:
# hpvmcreate -P guest -a dvd:avio_stor::disk:/dev/rdisk/disk5
# hpvmcreate -P guest -a dvd:avio_stor::null:/dev/rdisk/disk5
# hpvmmodify -P guest -a dvd:avio_stor::disk:/dev/rdisk/disk5
# hpvmmodify -P guest -a dvd:avio_stor::null:/dev/rdisk/disk5
9.1.3.1 Resource syntax
AVIO storage requires the hardware path of the lunpath class (displayed only in ioscan with the
-N option) to be specified in place of device special files in a resource specifier. Here is the syntax
of the resource specifier:
tape|changer|burner:avio_stor:bus,device,target:attach_path:new style
lunpath hardware path of the attached device
The following example shows the resource specifier with the avio_stor adapter:
tape:avio_stor:0,4,0:attach_path:0/7/1/1.0x500104f00048b29e.0x0
9.1 Introduction to vParVM storage 109