Limitations And Considerations; Aix 5L Version 5.3 Virtual I/O Server And Client Partitions - IBM p5 590 System Handbook

Internal or External Internal or External
Storage Storage
Figure 3-12 AIX 5L Version 5.3 Virtual I/O Server and client partitions

3.6.1 Limitations and considerations

The following areas should be considered when implementing virtual SCSI:
At the time of writing virtual SCSI supports Fibre Channel, parallel SCSI, and
SCSI RAID devices. Other protocols such as SSA or tape and CD-ROM
devices are not supported.
Virtual SCSI itself does not have any limitations in terms of number of
supported devices or adapters. At the time of writing, the Virtual I/O Server
supports a maximum of 1024 virtual I/O slots on an IBM Sserver p5 server.
A maximum of 256 virtual I/O slots can be assigned to a single partition.
Every I/O slot needs some resources to be instantiated. Therefore, the size of
the Virtual I/O Server puts a limit to the number of virtual adapters that can be
configured.
The SCSI protocol defines mandatory and optional commands. While virtual
SCSI supports all the mandatory commands, not all optional commands are
supported. You can find a complete list of the supported SCSI commands in
following publication: Advanced POWER Virtualization on IBM p5 Sserver
Introduction and Basic Configuration
There are performance implications when using virtual SCSI devices. It is
important to understand that associated with POWER Hypervisor calls, virtual
SCSI will use additional CPU cycles when processing I/O requests. When
putting heavy I/O load on virtual SCSI devices, this means you will use more
IBM Eserver p5 590 and 595 System Handbook
82
Physical Adapter Physical Adapter
VSCSI Server Virtual Adapter VSCSI Server Virtual Adapter
VSCSI Client Virtual Adapter VSCSI Client Virtual Adapter
I/O SERVER I/O SERVER I/O CLIENT I/O CLIENT
POW ER HYPERVISOR POW ER HYPERVISOR
,
SG24-7940.
I/O CLIENT I/O CLIENT I/O CLIENT I/O CLIENT