306 IBM eX5 Implementation Guide7.3 Memory considerationsSection 4.8, “Memory” on page 131 covers all of the various technical considerationsregarding memory configuration for the System x3690 X5. There is a great deal of flexibilityregarding the memory configuration of this server. As a result, there is a chance that youmight configure a less than optimal memory environment.Before you begin this section, understand how you are going to use the server. File serversthat are used to provide access to disk storage for other servers or workstations are lessaffected by a less perfect memory latency speed than a database or mail server. Servers thatare used as processing nodes in a high-performance cluster, database servers, or printservers for graphics printers require the best memory performance possible.7.3.1 Local memory installation considerationsThe following list describes considerations when installing memory inside the System x3690X5: When installing memory for two processors and no mezzanine, only processing threadsassigned to processor 2 will experience a 50% increase in memory latency. For a serverwith heavy I/O processing, this latency does not degrade the overall performance of theserver.Both processors 1 and 2 are installedMemory installed only on the systemboard (no memory mezzanine).Minimum of 2 DIMMs. Performance improves as DIMMs are added to evenlypopulate all ranks on each memory controller. Processing threads assigned to processor 2 will alwayshave a significant drop in performance formemory-intensive tasks. Not an operational configuration for OSs, such asVMware.Memory installed on both the systemboard and the mezzanine memoryboard. Performance improves as DIMMs are added to evenlypopulate all ranks on each memory controller. If processor 2 fails, memory on the memory mezzanineboard is unusable. This configuration is only an operational configurationfor VMware when both the system board and mezzaninememory board have the exact same total memoryinstalled. For ease of maintenance, the best practice isto have an identical memory configuration on both thesystem and mezzanine memory board.Memory installed on the systemboard, the mezzanine memory board,and the MAX5. Performance improves as DIMMs are added to evenlypopulate all ranks on each memory controller for localmemory. Performance is significantly improved when more activememory calls are using local memory on the systemboard instead of the memory located in the MAX5. In the rare instance of a mezzanine failure, VMwareoperational requirements can be satisfied if all of thememory is installed in the MAX5. Memory access will besignificantly slower if all of the memory is in the MAX5.Memory installed Operational characteristics
