Dell PowerEdge 2900 - Manual (Page 84)

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Installing System Components
General Memory Module Installation Guidelines
To ensure optimal performance of your system, observe the following guidelines when configuring your
system memory.
• Use only qualified FBDs. FBDs can be either single-ranked or dual-ranked. FBDs marked with a 1R
are single-ranked and modules marked with a 2R are dual-ranked.
• A minimum of two identical FBDs must installed.
• DIMM sockets must be populated by lowest number first.
• FBDs must be installed in pairs of matched memory size, speed, and technology, and the total
number of FBDs in the configuration must total two, four, eight, or twelve. For best system
performance, all four, eight, or twelve FBDs should be identical memory size, speed, and technology.
• Memory sparing and memory mirroring require eight or twelve FBDs, and all FBDs must be of
identical memory size, speed, and technology.
• Memory sparing and memory mirroring cannot be implemented at the same time.
Non-Optimal Memory Configurations
System performance can be affected if your memory configuration does not conform to the preceding
installation guidelines. Your system may issue an error message during startup stating that your memory
configuration is non-optimal.
Memory Sparing Support
The system supports memory sparing if eight or twelve identical memory modules are installed in the
system. The memory sparing feature must be enabled in the System Setup program and can be used only
if memory mirroring is not enabled.
Memory sparing allocates four ranks of DIMM memory to the spare bank of memory sparing. These four
ranks consist of the first rank of memory in DIMM sockets 1 through 4. For single-rank DIMMs, the
entire capacity of the four DIMMs is allocated to sparing whereas for dual-rank DIMMs, only half of the
four-DIMM capacity is allocated to sparing. Table 3-1 shows how memory sparing splits the available and
spared memory in each of the single- and dual-ranked memory module combinations.
Table 3-1. Memory Sparing Configurations
DIMMs Size/Type Total Memory Available Spare
8 256-MB single-rank 2 GB 1 GB 1 GB
512-MB single-rank 4 GB 2 GB 2 GB
1-GB single-rank 8 GB 4 GB 4 GB
2-GB single-rank 16 GB 8 GB 8 GB
2-GB dual-rank 16 GB 12 GB 4 GB
4-GB dual-rank 32 GB 24 GB 8 GB