Mirrored Memory - HP ProLiant ML370 Generation 5 User Manual

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 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 downtime.
Online spare is performed per memory board. For dual memory board configurations, two ranks are
used for online spare memory. One memory board can fail over to the associated online spare while the
other memory board is still protected.
In addition to general configuration requirements
spare memory has the following FBDIMM configuration requirements:
•
When only bank A on any memory board is populated, it must be fully populated with dual-rank
FBDIMMs.
•
For dual memory board configurations, each memory board must have a valid online spare FBDIMM
configuration. It is supported to have memory board 2 unpopulated while memory board 1 has a
valid online spare configuration.
•
For optimum memory usage, HP recommends all DIMMs on a memory board be the same size with
the same HP part number. If different sized DIMMs are used on a memory board, a portion of the
installed memory may not be utilized.
•
For dual memory board configurations, the FBDIMM part numbers on memory board 1 are not
required to match those installed on memory board 2
In online spare mode, each installed memory board must have an FBDIMM configuration as specified in
the following table:
Online spare memory configurations (per memory board):
Memory board
configuration
1
2
3
4
* Bank A must be populated with dual-rank FBDIMMs to support these configurations.
After installing FBDIMMs, use RBSU to configure the system for online spare memory support
("Configuring online spare

Mirrored memory

Mirroring provides protection against uncorrectable memory errors that would otherwise result in server
downtime. This protection is available without any operating system support.
Mirroring is performed on the memory board level. Memory board 1 and memory board 2 mirror each
other.
Each memory board maintains a copy of all memory contents. Memory writes go to both memory boards.
Memory reads come from only one of the two memory boards (unless an uncorrectable error occurs). If a
Bank A Bank B
1A and 5A* 2B and 6B
X —
X X
X X
X X
memory" on page 83).
("FBDIMM installation guidelines" on page 48), online
Bank C
3C and 7C
—
—
X
X
Bank D
4D and 8D
—
—
—
X
Hardware options installation 45