HP ProLiant ML350 G5 Server - Manual (Page 37)

Hardware options installation 37
Configuration Bank A
1A and 5A
Bank B
2B and 6B Bank C
3C and 7C Bank D
4D and 8D
1 X — — —
2 X X — —
3 X X X —
4 X X X X
Online spare memory configuration
Online spare memory provides protection against degrading FBDIMMs by reducing the likelihood of
uncorrectable memory errors.
An understanding of single-rank and dual-rank FBDIMMs is required to understand memory usage in
online spare mode. FBDIMMs can either be single-rank or dual-rank. Certain FBDIMM configuration
requirements are based on these classifications. A dual-rank FBDIMM is similar to having two separate
FBDIMMs, or ranks, on the same module. Although only a single FBDIMM module, a dual-rank FBDIMM
acts as two separate FBDIMMs. The purpose of dual-rank FBDIMMs is to provide the largest capacity
FBDIMM for the current DRAM technology. If the current DRAM technology allows for 2-GB single-rank
FBDIMMs, a dual-rank FBDIMM using the same technology would be 4-GB.
In online spare mode, a single rank of memory acts as the spare memory. For single-rank FBDIMMs, the
entire FBDIMM acts as the spare memory. For a dual-rank FBDIMM, only half of the FBDIMM acts as the
spare memory while the other half is available for operating system and application usage.
If one of the non-spare FBDIMMs receives correctable memory errors at a higher rate than a specific
threshold, the server automatically copies the memory contents of the degraded rank to the online spare
rank. The server then deactivates the failing rank and automatically switches over to the online spare.
Because FBDIMMs that experience a high rate of correctable memory errors have a higher probability of
receiving an uncorrectable memory error, this effectively reduces the likelihood of uncorrectable memory
errors that would result in server downtime.
Online spare FBDIMM configuration requirements (in addition to general configuration requirements):
• When only bank A is being used, it must be fully populated with dual-rank FBDIMMs.
• For optimum memory usage, HP recommends all FBDIMMs be the same size with the same HP part
number. If different sized FBDIMMs are used, a portion of the installed memory may not be utilized.
In online spare mode, FBDIMMs must be populated as specified in the following table:
Configuration Bank A
1A and 5A
Bank B
2B and 6B Bank C
3C and 7C Bank D
4D and 8D
1* X — — —
2 X X — —
3 X X X X
* Configuration 1 is only supported if using bank A, populated with dual-rank FBDIMMs.
After installing FBDIMMs, use RBSU to configure the system for online spare memory support.
Installing FBDIMMs