HP ProLiant BL480c Server-Blade - Manual (Page 34)

Hardware options installation 34
Configuration Bank A
1A , 4A Bank B
7B, 10B Bank C
2C, 5C Bank D
8D, 11D Bank E
3E, 6E Bank F
9F, 12F
6 X X X X X X
After installing FBDIMMs, use RBSU to verify the that the server blade is configured for Advanced ECC
operation.
Online spare memory configuration
Online spare memory provides protection against degrading FBDIMMs by reducing the likelihood of
uncorrectable memory errors. This protection is available without any operating system support.
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 single-rank
FBDIMMs 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 blade automatically copies the memory contents of the degraded rank to the online
spare rank. The server blade then deactivates the failing rank and automatically switches over to the
online spare. Because FBDIMMs that experience a high rate of correctable memory errors also have a
higher probability of receiving an uncorrectable memory error, this configuration reduces the likelihood of
uncorrectable memory errors that would result in server blade downtime.
Online spare is performed per branch of the memory controller. For a server blade with both branches
populated, two ranks are used for online spare memory. One branch can fail over to the associated
online spare while the other branch is still protected.
Each branch is made up of three banks:
• Branch 0 contains banks A, C, and E
• Branch 1 contains banks B, D, and F
In addition to general configuration requirements, online spare FBDIMM configuration also has the
following requirements:
• Banks A, C, and E must be fully populated with FBDIMMs with identical part numbers.
• Banks B, D, and F must contain FBDIMMs with identical part numbers, if installed.
For online spare mode, populate the FBDIMM slots as specified in the following table:
Configuration Branch 0
Bank A
1A, 4A
Branch 0
Bank C
2C, 5C Branch 0
Bank E
3E, 6E Branch 1
Bank B
7B, 10B Branch 1
Bank D
8D, 11D Branch 1
Bank F
9F, 12F
1 X X — — — —
2 X X X — — —
3 X X — X X —
4 X X X X X —
5 X X X X X X