Performance Tuning, Achieving Maximum Performance; Conclusion - HP 226824-001 - ProLiant - ML750 Introduction Manual

Performance tuning, achieving maximum performance

HP ProLiant servers implement a multi-branch memory architecture to reduce latency and enhance
performance. This architecture allows the memory controller to fetch data in parallel from the different
channels through memory interleaving. The latency for two channels is almost 40 percent lower than
that of a single channel. The difference in latency between two channels and four channels is not as
significant.
Figure 7 shows a dual-branch memory subsystem architecture using FB-DIMMs. To achieve maximum
performance, all FB-DIMMs should be installed in matching sockets across each paired channel. For
example, the FB-DIMM in slot 1A must be the same type (size and rank) as the FB-DIMM in slot 3A.
Likewise, the FB-DIMMs in slots 2B and 4B must be the same type. While single- and dual-rank FB-
DIMMs can be installed in a specific server, single-rank and dual-rank FB-DIMMs should not be mixed
in matching dual-channel sockets.
Figure 7. FB-DIMM population rules
General performance tuning tips include the use of dual-rank DIMMs and balanced channels. Use
dual-rank DIMMs instead of single-rank DIMMs if possible. For example, using eight 1-GB DIMMs
instead of sixteen 512MB DIMMs will improve performance. This has the added benefit of using less
power per GB of memory. Also, when configuring memory, keep the channels balanced to minimize
the latency per channel—latency increases with each additional set of FB-DIMMs.

Conclusion

HP supports the FB-DIMM standard because it increases reliability, bandwidth, and capacity while
using cost optimized, industry-standard DRAM components. The balanced system architecture of
ProLiant servers with dual-core processors and FB-DIMMs delivers increased memory capacity and
bandwidth. FBDIMM technology also delivers improved reliability through better data protection and
data availability.
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.
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