HP SAS DL360 - Manual (Page 45)

Hardware options installation 45
NOTE: When configuring the memory sub-system to run in Online
Spare mode, only single rank DIMMs can be installed in the system.
Online Spare Mode will not work with dual rank DIMMs installed in the
system.
DIMM guidelines
Observe the following DIMM installation guidelines:
• All DIMMs must be PC2-3200 DDR2 SDRAM DIMMs.
• Both DIMM slots in a memory bank must be populated.
• Both DIMMs in a memory bank must be identical.
• If mixing dual- and single-rank DIMMs, the dual-rank DIMMs must be
installed in memory bank 1.
Single- and dual-rank DIMMs
PC2-3200 DIMMs can either be single- or dual-rank. While it is not normally
important for you to differentiate between these two types of DIMMs, certain
DIMM configuration requirements are based on these classifications.
Certain configuration requirements exist with single- and dual-rank DIMMs that
allow the architecture to optimize performance. A dual-rank DIMM is similar to
having two separate DIMMs on the same module. Although only a single DIMM
module, a dual-rank DIMM acts as if it were two separate DIMMs. The primary
reason for the existence of dual-rank DIMMs is to provide the largest capacity
DIMM given the current DIMM technology. If the maximum DIMM technology
allows for creating 2-GB single-rank DIMMs, a dual-rank DIMM using the same
technology would be 4-GB.
Online spare memory configuration
With online spare memory, you can configure primary server memory for up to
6-GB of ECC DDR2 SDRAM and configure an additional 6-GB of online spare
memory. In this configuration, all six DIMM slots are populated with up to 2-GB
Registered ECC DDR2 SDRAM DIMMs.