Memory mirroring
This section contains information pertaining to the mirrored-channel mode of operation.
In the mirrored-channel mode, the channels are paired, and both channels in a pair store the same data. Memory-mirroring replicates and stores data on DIMMs across two or four channels simultaneously. If a failure occurs, the memory controller switches from the DIMMs on the primary channel to the DIMMs on the backup channel. To enable memory mirroring through the Setup utility, select System Settings → Memory → Memory Mode.
For more information, see Using the Setup utility.
When you use the memory mirroring mode, consider the following information:
- The server supports single-socket memory mirroring. Memory channel 0 mirrors channel 1, and memory channel 2 mirrors channel 3. This mirroring provides redundancy in memory but reduces the total memory capacity in half.
- DIMMs must be installed in pairs for each microprocessor when using the memory mirroring feature.
- The DIMM population must be identical for memory channel 0 and memory channel 1, and identical for memory channel 2 and memory channel 3.
- 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.
The following table lists the DIMM installation sequence for the memory-mirroring mode.
| DIMMs | Number of microprocessors | DIMM connector population sequence on the system board | DIMM connector population sequence on the optional microprocessor and memory expansion tray |
|---|---|---|---|
| One microprocessor | |||
| 1st pair | 1 | 1, 4 | |
| 2nd pair | 1 | 9, 12 | |
| 3rd pair | 1 | 2, 5 | |
| 4th pair | 1 | 8, 11 | |
| 5th pair | 1 | 3, 6 | |
| 6th pair | 1 | 7, 10 | |
| Two microprocessors | |||
| 1st set | 2 | 1, 4, 13, 16 | |
| 2nd set | 2 | 9, 12, 21, 24 | |
| 3rd set | 2 | 2, 5, 14, 17 | |
| 4th set | 2 | 8, 11, 20, 23 | |
| 5th set | 2 | 3, 6, 15, 18 | |
| 6th set | 2 | 7, 10, 19, 22 | |
| Four microprocessors | |||
| 1st set | 4 | 1, 4, 13, 16 | 25, 28, 37, 40 |
| 2nd set | 4 | 9, 12, 21, 24 | 33, 36, 45, 48 |
| 3rd set | 4 | 2, 5, 14, 17 | 26, 29, 38 41 |
| 4th set | 4 | 8, 11, 20, 23 | 32, 35, 44, 47 |
| 5th set | 4 | 3, 6, 15, 18 | 27, 30, 39, 42 |
| 6th set | 4 | 7, 10, 19, 22 | 31, 34, 43, 46 |
Note The server does not support a configuration of three microprocessors. The server supports one, two, or four microprocessors only. | |||