Chapter 4. IBM System x3690 X5 139MAX5 memory as seen by the operating systemMAX5 is capable of two modes of operation in terms of the way that memory is presented tothe operating system: Memory in MAX5 can be split and assigned between the CPUs on the host system(Non-Pooled mode). This mode is the default. Memory in MAX5 can be presented as a pool of space that is not assigned to anyparticular CPU (Pooled mode).By default, MAX5 is set to operate in partitioned mode because certain operating systemsbehave unpredictably when presented with a pool of memory space. Linux can work withmemory that is presented either as a pool or pre-assigned between CPUs; however forperformance reasons, if you are running Linux, change the setting to pooled mode. VMwarerequires that the MAX5 memory is in non-pooled mode.You can change this default setting in Unified Extensible Firmware Interface (UEFI). See 7.8,“UEFI settings” on page 337 for details.4.8.4 Memory balanceThe Xeon 7500 Series processor uses a nonuniform memory access (NUMA) architecture,as described in 2.3.4, “Nonuniform memory architecture (NUMA)” on page 26. BecauseNUMA is used, it is important to ensure that all memory controllers in the system are utilizedby configuring all processors with memory. Populating all processors in an identical fashion isoptimal to provide a balanced system and also required by VMware.Looking at Figure 4-17 on page 140 as an example, Processor 0 has DIMMs populated, butno DIMMs are populated that are connected to Processor 1. In this case, Processor 0 hasaccess to low latency local memory and high memory bandwidth. However, Processor 1 has4 20 and 215 26 and 316 11 and 147 3 and 68 18 and 239 27 and 3010 10 and 1511 2 and 712 19 and 2213 25 and 3214 12 and 1315 4 and 516 17 and 24VMware vSphere support: MAX5 requires VMware vSphere 4.1 or later.DIMM pair DIMM slot
