HP BL260c Memory technology evolution: an overview of system memory technologi - Page 23

Importance of using HP-certified memory modules in ProLiant servers There are several reasons why customers should use only HP memory option kits to replace or add memory in ProLiant servers. This section describes three of the most important reasons. First, not all DIMMs are created equal: They can vary greatly in quality and reliability. In the highly competitive memory market, some third-party memory resellers forego the level of qualification and testing needed for servers because it adds to the price of DIMMs. HP uses proprietary diagnostic tools and specialized server memory diagnostic tests that exceed industry-standards to ensure the highest level of performance and availability for ProLiant servers. The costs of system downtime, data loss, and reduced productivity caused by lower quality memory are far greater than the price difference between HP-certified memory and third-party DIMMs. Second, HP offers three levels of Advanced Memory Protection (AMP) that go beyond error correction to increase the fault tolerance of HP ProLiant servers. These AMP technologies-Online Spare Memory, Mirrored Memory, and Lockstep Memory-are optimized for each server series. For ProLiant servers with AMP, the DIMM configuration requirements are determined by the AMP mode selected. The HP memory option kits available for these servers prevent the violation of the configuration requirements for each AMP mode. Third, using HP memory option kits prevents improper mixing of single-, dual-, and quad-rank DIMMs. Although DIMMs of different ranks may have the same capacity, they differ in the way the memory controller accesses them (see the "DIMM configurations" section). Therefore, to ensure that the server boots properly and operates reliably, the DIMM loading of each channel should be consistent as to rank level. On the other hand, some ProLiant server platforms have configuration guidelines that allow the mixing of single-rank and dual-rank DIMMs. HP memory option kits precisely match the capabilities and requirements of the ProLiant server for which they are designated. HP memory option kits are listed in each server's user guide and in the product QuickSpecs available at www.hp.com. Conclusion The increasing performance gap between processors and memory has generated development of several memory technologies. While some memory manufacturers prefer a revolutionary approach to memory technology development, others favor an open, evolutionary approach. Memory manufacturers must balance the cost of performance enhancements against the laws of physics and compatibility with existing technologies. HP will continue to evaluate relevant memory technologies in order to offer customers products with the most reliable, best performing memory at the lowest possible cost. 23