IBM 787264U User Manual - Page 7

Optimized for virtualization and database applications with maximum memory and compute capacity in a blade DDR3 Registered Memory with Active Memory Protection The HX5 uses registered double data rate III (DDR3) VLP (very-low-profile) DIMMs and provides Active Memory features, including advanced Chipkill memory protection, for up to 16X better error correction than standard ECC memory. In addition to offering triple the memory bandwidth of DDR2 or fully-buffered memory, DDR3 memory also uses less energy. DDR2 memory already offered up to 37% lower energy use than fully buffered memory. Now, a generation later, DDR3 memory is even more efficient, using 10-15% less energy than DDR2 memory. The HX5 supports up to 128GB of memory in 16 DIMM slots. Redesign in the architecture of the Xeon 7500 series processors bring radical changes in the way memory works in these servers. For example, the 7500 series processors integrate 2 memory controllers inside each processor, resulting in four memory controllers in a two-socket system. Each memory controller has four memory channels, one per pair of DIMMs. Depending on the type of memory, population of memory, and processor model, the memory may be clocked at 978MHz or 800MHz. Adding a second HX5 server to the first doubles the memory capacity to 256GB in 32 DIMM slots. Redesign in the architecture of the x7500 series processors bring radical changes in the way memory works in these servers. For example, the Xeon 7500 series processors integrate two memory controllers inside each processor, resulting in four memory controllers in a twosocket system. Each processor has four memory channels. Note: If only one processor is installed, only eight DIMM slots (up to 64GB) can be used. There are two ways to expand memory beyond 8 DIMMs. Adding a second processor not only doubles the amount of memory available for use, but also doubles the number of memory controllers, thus doubling the system memory bandwidth. If you add a second processor, but no additional memory for the second processor, the second processor has to access the memory from the first processor "remotely," resulting in longer latencies and lower performance. The latency to access remote memory is almost 75% higher than local memory access. So, the goal should be to always populate both processors with memory. Alternatively, you can add a MAX5 memory expansion blade, containing 24 more DIMM slots with up to 192GB of memory. This offers up to 32 DIMMs and 256GB of memory with only a single processor. Adding the second processor allows the use of 8 more DIMM slots inside the HX5 and a grand total of 40 DIMMs and 320GB of memory in a double-wide (60mm) blade server. Using a MAX5 unit also boosts memory performance to 1066MHz for the server. SMI 1 SMI 2 SMI 3 SMI 4 SMI 5 SMI 6 SMI 7 SMI 8 Mill Brook 8 Mill Brook 7 Mill Brook 6 Mill Brook 5 Mill Brook 4 Mill Brook 3 Mill Brook 2 Mill Brook 1 Memory Controller-4 Memory Controller-3 Memory Controller-2 Memory Controller-1 QPI 24MB QL3PCI ache 24MB L3 Cache QPI (x4) CCCCCCCC or or or or or or or or e e e e e e e e CCCCCCCC or or or or or or or or e e e e e e e e Notes: DIMMs must be installed in matching pairs. Also, each CPU requires at least 2 DIMMs. It is important to ensure that all memory channels in each processor are populated. The relative memory bandwidth decreases as the number of channels populated decreases. This is because the bandwidth of all the memory channels is utilized to support the capability of the processor. So, as the channels are decreased, the burden to support the requisite bandwidth is increased on the remaining channels, causing them to become a bottleneck. For peak performance: • Always populate processors with equal amounts of memory to enable a balanced NUMA system • Always populate both memory channels on each processor with equal memory capacity • Ensure an even number of ranks are populated per channel Power guidelines: • Fewer larger DIMMs (for example 8 x 4GB DIMMs vs. 16 x 2GB DIMMs will generally have lower power requirements • x8 DIMMs (x8 data width of rank) will generally draw less power than equivalently sized x4 DIMMs Reliability guidelines: • Using fewer, larger DIMMs (for example 8 x 4 GB DIMMs vs. 16 x 2GB DIMMs is generally more 7. Please see the Legal Information section for important notices and information.