Lenovo ThinkSystem SR860 Setup Manual page 80

Memory sparing
In memory-sparing mode, one memory rank serves as a spare for other ranks on the same channel in case
they fail. The spare rank is held in reserve and not used as active memory until a failure is indicated, with
reserved capacity subtracted from the total available memory in the system. The DIMM installation order for
memory sparing varies based on the number of processors and memory modules installed in the server.
After an error threshold is surpassed in a system protected by memory sparing, the content of a failing rank
of DIMMs is copied to the spare rank. The failing rank is then taken offline and the spare rank placed online
for use as active memory in place of the failed rank. Since the failover process involves copying of memory
content, the level of memory redundancy provided by memory sparing is less than that provided by memory
mirroring: memory mirroring is the preferred failure-protection choice for critical applications.
Figure 48. Processor and memory module layout: processor 1 and 2
Table 52. Processor and memory module layout: processor 1 and 2
DIMM 1-6
1
DIMM 19-24
2
Processor 2
3
ThinkSystem SR860 Setup Guide
72
DIMM 7-18
4
Processor 1
5