Memory 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:

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

The following table shows the sequence of populating memory modules for mirroring mode.

Note

Thirty-two memory modules are required for configurations utilizing 64 GB (2Rx4) or 96 GB (2Rx4).
Sixteen or thirty-two memory modules are required for configurations utilizing 128 GB (2Rx4).

Table 1. Mirroring mode
Total DIMMs	Processor 1
Total DIMMs	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16
16 DIMMs ^{1, 2}	1		3		5		7			10		12		14		16
32 DIMMs ^{1, 2}	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16
Total DIMMs	Processor 2
Total DIMMs	17	18	19	20	21	22	23	24	25	26	27	28	29	30	31	32
16 DIMMs ^{1, 2}	17		19		21		23			26		28		30		32
32 DIMMs ^{1, 2}	17	18	19	20	21	22	23	24	25	26	27	28	29	30	31	32

Note

DIMM configurations that support the Sub NUMA Clustering (SNC) feature, which can be enabled via UEFI. SNC is not supported if DIMM population does not follow the sequence indicated by the table above.
DIMM configurations that support Software Guard Extensions (SGX), see Enable Software Guard Extensions (SGX) to enable this feature.

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