IBM p5 550 Technical Overview And Introduction

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Contents

Chapter 2. Architecture and technical overview 35Virtual SCSIAccess to real storage devices is implemented through the Virtual SCSI services, a part of theVirtual I/O Server partition. Logical volumes created and exported on the Virtual I/O Serverpartition will be shown at the Virtual Storage Client partition as a SCSI disk. All currentstorage device types, such as SAN, SCSI, and RAID, are supported. iSCSI and SSA are notsupported.2.10.3 Partition Load ManagerThe Partition Load Manager (PLM) provides automated processor and memory distributionbetween dynamic LPAR and Micro-partition-capable logical partition running AIX 5L. ThePLM application is based on a client/server model to share system information, such asprocessor or memory events, across the concurrent present logical partitions.To improve the overall resource utilization of a partitioned system, PLM uses user-definedresource management policies to determine the additional resources, such as processorsand memory, for each requesting partition.PLM uses the Resource Monitoring and Control (RMC) subsystem for networkcommunication, which provides several events on every managed Micro-partition node. Thefollowing 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 thresholdTo ensure a secure communication between managed Micro-partition nodes, OpenSSH andKerberos V5 are supported in PLM to have a secure communication and an authenticationmechanism for administrators. If Kerberos is not installed, PLM uses the next configuredauthentication method, such as AIX authentication.2.10.4 Simultaneous multi-threadingAs a permanent requirement for performance improvements at the application level,simultaneous multi-threading (SMT) functionality is embedded in the POWER5 chiptechnology. Developers are familiar with process-level parallelism (multi-tasking) andthread-level parallelism (multi-threads). SMT is the next stage of processor saturation forthroughput-oriented applications to introduce the method of instruction-level parallelism tosupport multiple pipelines to the processor.By default, SMT is activated. On a 2-way POWER5 processor-based system, the operatingsystem views the available processors as a 4-way system. To achieve a higher performancelevel, SMT is also applicable in Micro-Partitioning, capped or uncapped, and dedicatedpartition environments.Simultaneous multi-threading is supported on POWER5 systems running AIX 5L V5.3 orLinux operating system-based at a required 2.6 kernel. AIX provides the smtctl commandthat turns SMT on and off without a subsequent reboot. For Linux, an additional boot optionmust be set to activate SMT after a reboot.Note: The Shared Ethernet adapter and Virtual SCSI server function is provided in theVirtual I/O Server that is included in the optional Advanced POWER Virtualization feature.