Dell PowerEdge 2900 Hardware Owner's Manual (PDF) - Page 84

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 8 Size/Type 256-MB single-rank 512-MB single-rank 1-GB single-rank 2-GB single-rank 2-GB dual-rank 4-GB dual-rank Total Memory 2 GB 4 GB 8 GB 16 GB 16 GB 32 GB Available 1 GB 2 GB 4 GB 8 GB 12 GB 24 GB Spare 1 GB 2 GB 4 GB 8 GB 4 GB 8 GB 84 Installing System Components