Memory mirroring

Memory-mirroring mode replicates and stores data on two pairs of DIMMs within two channels simultaneously.

Memory-mirroring mode replicates and stores data on two pairs of DIMMs within two channels simultaneously. If a failure occurs, the memory controller switches from the primary pair of memory DIMMs to the backup pair of DIMMs. You must enable memory mirroring through the Setup utility. For details about enabling memory mirroring, see Using the Setup utility. When you use the memory mirroring feature, consider the following information:

DIMMs must be installed in pairs. The DIMMs in each pair must be the same size and type.
The maximum available memory is reduced to one third of the installed memory when memory mirroring is enabled. For example, if you install 96 GB of memory, only 32 GB of addressable memory is available when you use memory mirroring.
Channel 1 DIMM connectors 1, 2, 7, and 8 are not used in memory-mirroring mode.

The following table lists the installation sequence for installing DIMMs in memory-mirroring mode.

Table 1. DIMM population sequence (memory-mirroring mode)
Number of installed microprocessors	DIMM connector population sequence
1	3, 5
1	4, 6
2	3, 5
	9, 11
	4, 6
	10, 12
Note DIMM connectors 1, 2, 7, and 8 are not used in memory-mirroring mode.

When you install or remove DIMMs, the server configuration information changes. When you restart the server, the system displays a message that indicates that the memory configuration has changed.

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