IBM BladeCenter PS703, Technical Overview And Introduction, Page: 124 / 198

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IBM BladeCenter PS703 and PS704 Technical Overview and Introduction
For a more detailed discussion about virtual networking, see the following web page:
http://www.ibm.com/servers/aix/whitepapers/aix_vn.pdf
Virtual SCSI
Virtual SCSI is provided by the POWER Hypervisor and provides a virtualized implementation
of the SCSI protocol. This implementation provides secure communication between the Client
partition (AIX, Linux, or IBM i) and the VIOS in a client/sever relationship. The VIOS logical
partition or virtual server owns the physical resources and acts as server for them or, in SCSI
terms, target devices. 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 SDMC or through IVM on POWER-based 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 as virtual disks.
򐂰 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 as well as disk devices.
Figure 3-12 on page 111 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 normal hdisk.
Note: An SEA does not need to have an IP address configured to perform the Ethernet
bridging functionality. Configuring an IP address is required to access the IVM.