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Memory mirrored channel

Memory mirrored channel 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. To enable memory mirrored channel through the Setup utility, select System Settings > Memory. For more information, see Using the Setup utility. When you use the memory mirrored channel feature, consider the following information:
  • When you use memory mirrored channel, you must install a pair of DIMMs at a time. The two DIMMs in each pair must be identical in size, type, and rank (single, dual, or quad), and organization, but not in speed. The channels run at the speed of the slowest DIMM in any of the channels.
  • The maximum available memory is reduced to half of the installed memory when memory mirrored channel is enabled. For example, if you install 64 GB of memory using RDIMMs, only 32 GB of addressable memory is available when you use memory mirrored channel.
  • For UDIMMs, DIMM connectors 3, 6, 7, and 10 for microprocessor 1 and DIMM connectors 15, 18, 19, and 22 for microprocessor 2 are not used in memory mirrored channel mode.

The following diagram lists the DIMM connectors on each memory channel.

Figure 1. Connectors on each memory channel
Connectors on each memory channel

The following table shows the installation sequence for memory mirrored channel mode:

Table 1. Memory mirrored channel mode DIMM population sequence.

Number of DIMMsNumber of installed microprocessorDIMM connector
First pair of DIMMs11, 4
Second pair of DIMMs19, 12
Third pair of DIMMs12, 5
Fourth pair of DIMMs18, 11
Fifth pair of DIMMs13, 6
Sixth pair of DIMMs17, 10
Seventh pair of DIMMs213, 16
Eighth pair of DIMMs221, 24
Ninth pair of DIMMs214, 17
Tenth pair of DIMMs220, 23
Eleventh pair of DIMMs215, 18
Twelfth pair of DIMMs219, 22
Note
DIMM connectors 3, 6, 7, 10, 15, 18, 19, and 22 are not used in memory mirrored channel mode when UDIMMs are installed in the server.