Mirroring mode installation order
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.
In mirroring mode, each memory module in a pair must be identical in size and architecture. The channels are grouped in pairs with each channel receiving the same data. One channel is used as a backup of the other, which provides redundancy.
All memory modules to be installed must be of the same type with the same capacity, frequency, voltage, and ranks.
Mirroring can be configured across channels in the same iMC, and the total TruDDR5 memory size of the primary and secondary channels must be the same.
9x4 RDIMMs do not support mirroring mode.
Partial Memory Mirroring is a sub-function of memory mirroring. It requires following the memory installation order of memory mirroring mode.
With one processor
The following table shows the sequence of populating memory modules for mirroring mode when only one processor is installed.
| Total DIMMs | Processor 1 | ||||||||||||||||
| 16 | 15 | 14 | 13 | 12 | 11 | 10 | 9 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | ||
| 8 DIMMs1,2 | 16 | 14 | 12 | 10 | 7 | 5 | 3 | 1 | |||||||||
| 16 DIMMs1,2 | 16 | 15 | 14 | 13 | 12 | 11 | 10 | 9 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | |
The DIMM configurations 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.
5600 MHz 24 GB and 48 GB RDIMMs are supported in 8 DIMMs mirroring mode, and all other RDIMMs are supported in 8 and 16 DIMMs mirroring mode.
Two processors
The following table shows the sequence of populating memory modules for mirroring mode when two processors are installed.
| Total DIMMs | Processor 1 | ||||||||||||||||
| 16 | 15 | 14 | 13 | 12 | 11 | 10 | 9 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | ||
| 16 DIMMs1,2 | 16 | 14 | 12 | 10 | 7 | 5 | 3 | 1 | |||||||||
| 32 DIMMs1,2 | 16 | 15 | 14 | 13 | 12 | 11 | 10 | 9 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | |
| Total DIMMs | Processor 2 | ||||||||||||||||
| 32 | 31 | 30 | 29 | 28 | 27 | 26 | 25 | 24 | 23 | 22 | 21 | 20 | 19 | 18 | 17 | ||
| 16 DIMMs1,2 | 32 | 30 | 28 | 26 | 23 | 21 | 19 | 17 | |||||||||
| 32 DIMMs1,2 | 32 | 31 | 30 | 29 | 28 | 27 | 26 | 25 | 24 | 23 | 22 | 21 | 20 | 19 | 18 | 17 | |
The DIMM configurations 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.
5600 MHz 24 GB and 48 GB RDIMMs are supported in 16 DIMMs mirroring mode, and all other RDIMMs are supported in 16 and 32 DIMMs mirroring mode.