Table 10. DIMM population sequence for independent memory mode (continued)DIMM installation orderIndependent mode withmemory mirroring disabledIndependent mode withmemory mirroring enabled23 DIMM connector 2124 DIMM connector 18Memory mirroringUse this information for an overview of memory mirroring.Memory-mirroring replicates and stores data on DIMMs across all four memorychannels for the compute book and DDR3 channels simultaneously. If a failureoccurs, the memory controller switches from the DIMMs on the primary channelsto the DIMMs on the backup channels. To enable memory mirroring through theSetup utility, select System Settings → Memory → Memory Mode. For moreinformation, see “Using the Setup utility” on page 126. For more information andnotes about installing DIMMs, see “Installing a memory module” on page 47. Formore information and the DIMM population sequence for memory mirroring, see“Memory mirroring in independent memory mode” on page 56 and “Memorymirroring in lockstep mode” on page 60.Memory mirroring is supported in independent mode and lockstep mode.When you use the memory mirroring feature, consider the following information:v The server supports single-socket memory mirroring. The compute bookmemory channel 0 mirrors memory channel 1, and memory channel 2 mirrorsmemory channel 3. This mirroring provides redundancy in memory but reducesthe total memory capacity in half.v DIMMs must be installed in pairs for each compute book when using thememory mirroring feature.v The DIMM population must be identical (size, organization, etc.) for memorychannel 0 and memory channel 1, and identical for memory channel 2 andmemory channel 3.v Memory mirroring reduces the maximum available memory by half of theinstalled memory. For example, if the server has 64 GB of installed memory, only32 GB of addressable memory is available when memory mirroring is enabled.Chapter 2. Installing optional devices 53
