Memory Fault Tolerance - IBM System x3850 X5 Implementation Manual

7.3.3 Memory fault tolerance

For servers with high availability requirements, using the memory mirroring or memory
sparing configuration allows the server to continue to function normally in the rare event of a
memory failure. See 2.3.6, "Reliability, availability, and serviceability (RAS) features" on
page 28 for an explanation of the memory mirroring and memory sparing functions.
Note, however, that considering that memory is like a solid-state device, it is unlikely that a
DIMM failure will occur outside of the first 90 days of operation. Statistically, there is a higher
risk for failure with power supplies, copper network adapters, storage devices, or processors.
High availability is almost always a desired goal, but for true high availability, consider a
cluster of host computers using common storage that allows virtual servers to be defined and
moved from one host server to another host server.
If high availability is the most important aspect of your server (with cost and performance as
secondary concerns), enable memory mirroring or memory sparing.
Use the following steps to establish memory mirroring or memory sparing:
1. Boot the server into F1-Setup.
2. From the System Configuration panel, select System Settings  Memory (Figure 7-8).
Figure 7-8 Memory configuration panel in F1-Setup
Figure 7-8 shows the Memory configuration panel with selections for performing memory
sparing or memory mirroring, but not both at the same time. Select the desired option and
reboot the server. If your memory population order does not support the requested option, the
server will report a memory configuration error during the next reboot.
See 4.8.2, "x3690 X5 memory population order" on page 133 for the correct memory
population order to support memory mirroring or sparing.
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IBM eX5 Implementation Guide