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Mirroring mode installation order

Memory-mirroring mode provides full memory redundancy while reducing the total system memory capacity in half. Memory channels are grouped in pairs with each channel receiving the same data. If a failure occurs, the memory controller switches from the DIMMs on the primary channel to the DIMMs on the backup channel. The DIMM installation order for memory mirroring varies based on the number of processors and DIMMs installed in the server.

Memory mirroring guidelines:
  • Memory mirroring reduces the maximum available memory by half of the installed memory. For example, if the server has 64 GB of installed memory, only 32 GB of addressable memory is available when memory mirroring is enabled.

  • Each DIMM must be identical in size and architecture.

  • DIMMs on each memory channel must be of equal density.

  • If two memory channels have DIMMs, mirroring occurs across two DIMMs (channels 0/1 will both contain the primary/secondary memory caches).

  • If three memory channels have DIMMs, mirroring occurs across all three DIMMs (channels 0/1, channels 1/2, and channels 2/0 will all contain primary/secondary memory caches).

  • Mixing DIMMs with different capacity is not allowed. All DIMMs installed must be identical.

  • Partial Memory Mirroring is a sub-function of memory mirroring. It requires following the memory installation order of memory mirroring mode.

Mirroring mode population sequence

SD650 V3 supports fully populated processors only (two processors per node)

Table 1. Mirroring mode memory population sequence
Processor 1Processor 2
Memory channel1010010110100101
DIMM slot number12345678910111213141516