Memory Mirroring; Rank Sparing - Lenovo System x3630 M4 Installation And Service Manual

Memory mirroring

Memory-mirroring mode replicates and stores data on two pairs of DIMMs within two channels
simultaneously.
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 "Using the Setup utility" on page 98. When you use the memory
mirroring feature, consider the following information:
• DIMMs must be installed in pairs. The DIMMs in each pair must be the same size and type.
• The maximum available memory is reduced to one third of the installed memory when memory mirroring
is enabled. For example, if you install 96 GB of memory, only 32 GB of addressable memory is available
when you use memory mirroring.
• Channel 1 DIMM connectors 1, 2, 7, and 8 are not used in memory-mirroring mode.
The following table lists the installation sequence for installing DIMMs in memory-mirroring mode.
Table 8. DIMM population sequence (memory-mirroring mode)
Number of installed microprocessors
1
2
Note: DIMM connectors 1, 2, 7, and 8 are not used in
memory-mirroring mode.
When you install or remove DIMMs, the server configuration information changes. When you restart the
server, the system displays a message that indicates that the memory configuration has changed.

Rank sparing

Sparing enables a failing rank to be replaced by ranks installed in an unoccupied space. An unused spare
rank on the channel can be used to copy the contents of a failing rank on that channel.
When you use the memory mirroring feature, consider the following information:
• In rank sparing mode, one rank of a DIMM in each populated channel is reserved as spare memory. The
spare rank is not available as active memory. When the active rank memory fails, its content is copied to
the spare rank memory which becomes active. The spare rank must have identical or larger memory
capacity than all the other ranks on the same channel.
• DIMMs must be installed in sets of three. The DIMMs in each set must be the same size and type.
• The following table lists the DIMM installation sequence for rank sparing mode when one or two
microprocessors is installed in the server:
The following table shows the installation sequence for installing DIMMs for each microprocessor in
memory online-spare mode:
70
Lenovo System x3630 M4 Installation and Service Guide
DIMM connector population sequence
3, 5
4, 6
3, 5
9, 11
4, 6
10, 12