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Installing System Components 101
•Memory sp
aring and
memory m
irroring require
e
ight 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 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.
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.
Memory Mirroring Support
The system supports memory mirroring if eight identical memory modules
are installed in the system. Mirroring must be enabled in the System Setup
program and can be used only if memory sparing is not enabled. In a mirrored
configuration, the total available system memory is one-half of the total
installed memory.
Table 3-1. Memory Sparing Configurations
DIMMs Size/Type Total Memory Available Spare
8 1-GB single-rank 8 GB 4 GB 4 GB
8 2-GB single-rank 16 GB 8 GB 8 GB
8 2-GB dual-rank 16 GB 12 GB 4 GB
Book.book Page 101 Monday, September 14, 2009 12:57 PM