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Virtual SCSI
Access to real storage devices is implemented through the Virtual SCSI services, a part of the
Virtual I/O Server partition. Logical volumes created and exported on the Virtual I/O Server
partition will be shown at the Virtual Storage Client partition as a SCSI disk. All current
storage device types, such as SAN, SCSI, and RAID, are supported. iSCSI and SSA are not
supported.
Note: The Shared Ethernet adapter and Virtual SCSI server function is provided in the
Virtual I/O Server that is included in the optional Advanced POWER Virtualization feature.
2.10.3 Partition Load Manager
The Partition Load Manager (PLM) provides automated processor and memory distribution
between dynamic LPAR and Micro-partition-capable logical partition running AIX 5L. The
PLM application is based on a client/server model to share system information, such as
processor or memory events, across the concurrent present logical partitions.
To improve the overall resource utilization of a partitioned system, PLM uses user-defined
resource management policies to determine the additional resources, such as processors
and memory, for each requesting partition.
PLM uses the Resource Monitoring and Control (RMC) subsystem for network
communication, which provides several events on every managed Micro-partition node. The
following events are registered on all managed Micro-partition nodes:
Memory-pages-steal high thresholds and low thresholds
Memory-usage-high thresholds and low thresholds
Processor-load-average high threshold and low threshold
To ensure a secure communication between managed Micro-partition nodes, OpenSSH and
Kerberos V5 are supported in PLM to have a secure communication and an authentication
mechanism for administrators. If Kerberos is not installed, PLM uses the next configured
authentication method, such as AIX authentication.
2.10.4 Simultaneous multi-threading
As a permanent requirement for performance improvements at the application level,
simultaneous multi-threading (SMT) functionality is embedded in the POWER5 chip
technology. Developers are familiar with process-level parallelism (multi-tasking) and
thread-level parallelism (multi-threads). SMT is the next stage of processor saturation for
throughput-oriented applications to introduce the method of instruction-level parallelism to
support multiple pipelines to the processor.
By default, SMT is activated. On a 2-way POWER5 processor-based system, the operating
system views the available processors as a 4-way system. To achieve a higher performance
level, SMT is also applicable in Micro-Partitioning, capped or uncapped, and dedicated
partition environments.
Simultaneous multi-threading is supported on POWER5 systems running AIX 5L V5.3 or
Linux operating system-based at a required 2.6 kernel. AIX provides the smtctl command
that turns SMT on and off without a subsequent reboot. For Linux, an additional boot option
must be set to activate SMT after a reboot.
Chapter 2. Architecture and technical overview
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