Memory Mirroring - Lenovo System x3750 M4 Installation And Service Manual

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" on page 134.
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.
Table 9. DIMM population sequence for memory mirroring mode
DIMMs
One microprocessor
1st pair
2nd pair
3rd pair
4th pair
5th pair
6th pair
Two microprocessors
1st set
2nd set
3rd set
4th set
5th set
6th set
Four microprocessors
1st set
Number of
microprocessors
1
1
1
1
1
1
2
2
2
2
2
2
4
DIMM connector
population sequence
on the system board
1, 4
9, 12
2, 5
8, 11
3, 6
7, 10
1, 4, 13, 16
9, 12, 21, 24
2, 5, 14, 17
8, 11, 20, 23
3, 6, 15, 18
7, 10, 19, 22
1, 4, 13, 16
Chapter 2
DIMM connector
population sequence
on the optional
microprocessor and
memory expansion tray
25, 28, 37, 40
.
Installing optional devices
49