IBM System x3850 X5 Installation And User Manual page 99

Table 12. Non-mirroring mode DIMM population sequence for the memory expansion
module
Pairs of DIMMs
Pair 1
Pair 2
Pair 3
Pair 4
Pair 5
Pair 6
Pair 7
Pair 8
Pair 9
Pair 10
Pair 11
Pair 12
Pair 13
Pair 14
Pair 15
Pair 16
Note: When you populate DIMMs in the memory expansion module,
populate the larger capacity DIMMs first, then the smaller capacity DIMMs.
– Memory-mirroring mode. When you use the mirroring mode feature,
consider the following information:
- Memory-mirroring mode replicates and stores data on sets of DIMMs
simultaneously. If a failure occurs, the memory controller switches from the
primary set of DIMMs to the backup set of DIMMs. To enable memory
mirroring through the Setup utility, select System Settings → Memory. For
more information, see "Using the Setup utility" on page 96.
- DIMMs must be installed in sets of four. The DIMMs in each set must be
the same size and type. This is applicable also when the memory expansion
module is attached to a host server and the host server has an optional
memory tray installed in the server. You must install DIMMs in sets of four
DIMMs for memory-mirroring mode in each (server, memory tray, and the
memory expansion module).
- The maximum available memory is reduced to half of the installed memory
when memory mirroring is enabled. For example, if the memory expansion
module has 64 GB of memory installed, only 32 GB of addressable memory
is available when you use memory mirroring.
- The following table lists the DIMM installation sequence for
memory-mirroring mode.
Table 13. Memory-mirroring mode DIMM population sequence for the memory expansion
module
Sets of 4 DIMMs
Set 1
Set 2
DIMM connector population sequence
28, 29
9, 16
1, 8
20, 21
26, 31
11, 14
3, 6
18, 23
27, 30
10, 15
2, 7
19, 22
25, 32
12, 13
4, 5
17, 24
DIMM connector population sequence
9, 16, 28, 29
1, 8, 20, 21
Chapter 2. Installing optional devices
85