Chapter 3. Virtualization
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Virtual SCSI
Virtual SCSI refers to a virtualized implementation of the SCSI protocol. Virtual SCSI is based
on a client/server relationship. The Virtual I/O Server logical partition owns the physical
resources and acts as a server or, in SCSI terms, a target device. The client logical partitions
access the virtual SCSI backing storage devices provided by the Virtual I/O Server as clients.
The virtual I/O adapters (virtual SCSI server adapter and a virtual SCSI client adapter) are
configured using a managed console or through the Integrated Virtualization Manager on
smaller systems. The virtual SCSI server (target) adapter is responsible for executing any
SCSI commands that it receives. It is owned by the Virtual I/O Server 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 Virtual I/O Server.
Physical disks presented to the Virtual/O Server can be exported and assigned to a client
partition in several 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.
As of Virtual I/O Server 1.5, files can be created on these disks, and file-backed storage
devices can be created.
The logical volumes or files can be assigned to separate partitions. Therefore, virtual SCSI
enables sharing of adapters and disk devices.
IP address: A Shared Ethernet Adapter does not need to have an IP address configured
to be able to perform the Ethernet bridging functionality. Configuring IP on the Virtual I/O
Server is convenient because the Virtual I/O Server can then be reached by TCP/IP, for
example, to perform dynamic LPAR operations or to enable remote login. This task can be
done either by configuring an IP address directly on the SEA device or on an additional
virtual Ethernet adapter in the Virtual I/O Server. This leaves the SEA without the IP
address, allowing for maintenance on the SEA without losing IP connectivity in case SEA
failover is configured.