Memory Mirroring - Lenovo ThinkServer RD220 Hardware Maintenance Manual

Important: If you have configured the server to use memory mirroring, do not use the order in DIMM
installation sequence for non-mirroring (normal) mode ; go to Memory mirroring and use the installation
order shown there.
Table 9. DIMM installation sequence for non-mirroring (normal) mode
Installed microprocessors
Microprocessor socket 1
Microprocessor socket 2

Memory mirroring

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 "Memory mirroring" on page 168. When you use the memory mirroring
feature, consider the following information:
• When you use memory mirroring, you must install a pair of DIMMs at a time. One DIMM must be in
channel 0, and the mirroring DIMM must be in the same connector in channel 1. The two DIMMs in each
pair must be identical in size, type, rank (single, dual, or quad), and organization. They do not have to
be identical in speed. The channels run at the speed of the slowest DIMM in any of the channels. See
Table 11 "Memory-mirroring mode DIMM population sequence" on page 169 for the DIMM connectors
that are in each pair.
• Channel 2, DIMM connectors 8 ,7, 15, and 16 are not used in memory-mirroring mode.
• The maximum available memory is reduced to half of the installed memory when memory mirroring is
enabled. For example, if you install 64 GB of memory, only 32 GB of addressable memory is available
when you use memory mirroring.
The following illustration shows the memory channel interface layout with the DIMM installation sequence
for mirroring mode. The numbers within the boxes indicate the DIMM population sequence in pairs within
the channels, and the numbers next to the boxes indicate the DIMM connectors within the channels. For
example, the following illustration shows that the first pair of DIMMs (indicated by ones (1) inside the
boxes) should be installed in DIMM connector 3 on channel 0 and DIMM connector 6 on channel 1. DIMM
connectors 7, 8, 15, and 16 on channel 2 are not used in memory-mirroring mode.
Figure 1. Memory channel interface layout
The following table lists the DIMM connectors on each memory channel.
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ThinkServer RD220 Hardware Maintenance Manual
DIMM connector population sequence
Install the DIMMs in the following sequence: 3, 6, 8, 2, 5, 7, 1, 4
Install the DIMMs in the following sequence: 11, 14, 16, 10, 13, 15, 9, 12