HP Integrity Virtual Machines Installation, Configuration, and Administration Version A.03.50

7.1.2.2 Attached I/O
Attached I/O allows a virtual machine to access to a VM Host LUN directly. In this architecture,
the Integrity VM storage subsystem attaches a LUN on the VM Host 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 VM Host and all the storage connected to those adapters
may be shared among virtual machines. In attached I/O, only the storage adapter is virtualized.
Therefore, only the VM Host physical storage adapters may be shared. At least one LUN, the
attached LUN, cannot be shared. It is owned and solely controlled by the virtual machine it is
attached to.
To provide the VM with complete control over attached devices, the Integrity VM storage
subsystem interprets I/O requests from the guest device drivers into I/O requests that can be
completed by the VM Host storage subsystem on the guest's behalf. In the process, the VM Host
storage subsystem sends all the actual data and responses back the guest device drivers. With
all this data, the guest device driver is in complete control over the device. As such, the guest
OS must have built-in support for the attached VM Host 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.
7.1.3 Integrity VM Storage Implementations
This section describes the implementations of the Integrity VM storage architectures.
7.1.3.1 Integrity VM Storage Adapters
Integrity VM provides a virtual PCI parallel SCSI MPT adapter to process virtual storage I/O
requests. All supported guest operating systems contain native MPT SCSI adapter drivers that
communicate with this PCI register emulation. All virtual and attachable devices can be used
with this single virtual storage adapter.
7.1.3.2 Integrity VM Storage Devices
Integrity VM supports a variety of virtual and attachable devices. Disk and DVD-ROM devices
support several virtual media types (see Section 7.1.3.2.1 (page 83)). Physical tapes, media
changers, and CD/DVD burners are attachable; they can be used to perform data backups directly
from a virtual machine (see Section 7.1.3.2.2 (page 84)).
7.1.3.2.1 Virtual Devices
Integrity VM supports the following virtual disk types:
For more information, see...Backing Storage DeviceVirtual Disk Type
Section 7.2.2.3.1: “Virtual Disks” (page 93)VM Host diskVirtual Disk
Section 7.2.2.3.2: “Virtual LvDisks” (page 94)VM Host LVM or VxVM logical
volume
Virtual LvDisk
Section 7.2.2.3.3: “Virtual FileDisks” (page 96)VM Host VxFS fileVirtual FileDisk
7.1 Introduction to Integrity VM Storage 83