Dell PowerEdge M620 Owner's Manual page 212

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 start-up stating that your memory configuration is non-
optimal.
Memory Sparing Support – PowerEdge M600
Memory sparing requires eight identical memory modules. The memory sparing
feature must also be enabled in the System Setup program, and can be used
only if memory mirroring is not enabled.
Table 3-15 shows how memory sparing splits the available and spared memory
in each memory module configuration.
Table 3-15. Memory Sparing Configurations
DIMMs Size/Type
8 512 MB
8 1 GB single-rank
8 2 GB dual-rank
8 4 GB dual-rank
Memory Mirroring Support – PowerEdge M600
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.
212
Installing Blade Components
–
PowerEdge M600
Total Memory
4 GB
8 GB
16 GB
32 GB
Available Spare
2 GB 2 GB
4 GB 4 GB
12 GB 4 GB
24 GB 8 GB