IBM PS700, Technical Overview And Introduction

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Chapter 3. Virtualization
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Virtual SCSI
As discussed earlier Virtual SCSI is provided by the POWER Hypervisor and allows secure
communication between Client partition (AIX, Linux, or IBM i) and the VIOS. The VIOS logical
partition owns the physical resources and acts as server or, in SCSI terms, target device. The
client logical partitions access the virtual SCSI backing storage devices provided by the VIOS
as clients.
The virtual I/O adapters (virtual SCSI server adapter and a virtual SCSI client adapter) are
configured using an HMC or through the IVM on Blade Servers. The virtual SCSI server
(target) adapter is responsible for executing any SCSI commands it receives. It is owned by
the VIOS partition. The virtual SCSI client adapter allows a client partition to access physical
SCSI and SAN attached devices and LUNs that are assigned to the client partition. The
provisioning of virtual disk resources is provided by the VIOS.
Physical disks presented to the VIOS can be assigned to a client partition in a number of
ways:
򐂰
The entire disk is presented to the client partition.
򐂰 The disk is divided into several logical volumes, which can be presented to a single client
or multiple clients.
The logical volumes or files can be assigned to separate partitions. Therefore, virtual SCSI
enables sharing of adapters as well as disk devices.
Figure 3-7 shows an example where one physical disk is divided into two logical volumes by
the VIOS. Each of the two client partitions is assigned one logical volume, which is then
accessed through a virtual I/O adapter (VSCSI Client Adapter). Inside the client partition, the
disk is seen as a regular hdisk.
Figure 3-7 Architectural view of virtual SCSI
VIRTUAL I/O Serer
Partition
Client Partition 2 Client Partition 1
Physical Adapter
POWER Hypervisor
Vscsi
Server
Adapter
Vscsi
Server
Adapter
Vscsi
Client
Adapter
Vscsi
Client
Adapter
Physical Disk
(SCI, FC)
Hdisk Hdisk
LVM
Logical
Volume 2
Logical
Volume 1