moved to the spare area while the operating system is running to
prevent errors from causing an uncorrectable failure. Requires
population of three ranks or more per channel.
With single rank memory sparing enabled, the system memory available to the operating system is reduced by one rank per channel. For
example, in a dual-processor configuration with twenty four 16 GB dual-rank memory modules, the available system memory is: 3/4 (ranks/
channel) × 24 (memory modules) × 16 GB = 288 GB, and not 24 (memory modules) × 16 GB = 384 GB. This calculation changes based on
if it is single rank sparing or multi rank sparing. For multi rank sparing, the multiplier changes to 1/2 (ranks/channel).
NOTE:
Memory sparing does not offer protection against a multi-bit uncorrectable error.
Memory mirroring
Memory mirroring offers the strongest memory module reliability mode, providing improved uncorrectable multi-bit failure protection. In a
mirrored configuration, the total available system memory is one half of the total installed physical memory. Half of the installed memory is
used to mirror the active memory modules. In the event of an uncorrectable error, the system switches over to the mirrored copy. This
ensures Single Device Data Correction (SDDC) and multi-bit protection.
The installation guidelines for memory modules are as follows:
•
Memory modules must be identical in size, speed, and technology.
•
Memory modules must be populated in sets of 6 per CPU to enable memory mirroring.
Table 29. Memory population rules
Processor
Configuration
Memory population
Memory population information
Dual CPU (Starting with
CPU1, CPU1 and CPU2
population should
match)
Optimized (Independent channel)
population order
C1{1}, C2{1}, C1{2}, C2{2}, C1{3},
C2{3}...
Odd amount of DIMM slots per CPU
allowed.
Mirroring population order
C1{1, 2, 3, 4, 5, 6}, C2{1, 2, 3, 4, 5,
6}, C1{7, 8, 9, 10, 11, 12}, C2{7, 8,
9, 10, 11, 12}
Mirroring is supported with 6 or 12
DIMM slots per CPU.
Single rank sparing population order C1{1}, C2{1}, C1{2}, C2{2}, C1{3},
C2{3}...
Populate in this order, odd amount per
CPU allowed. Requires two ranks or
more per channel.
Multi rank spare population order
C1{1}, C2{1}, C1{2}, C2{2}, C1{3},
C2{3}, C1{4}, C2{4}, C1{5},
C2{5}...
Populate in this order, odd amount per
CPU allowed. Requires three ranks or
more per channel.
Fault resilient population order
C1{1, 2, 3, 4, 5, 6}, C2{1, 2, 3, 4, 5,
6}, C1{7, 8, 9, 10, 11, 12}, C2{7, 8,
9, 10, 11, 12}
Supported with 6 or 12 DIMM slots
per CPU.
Removing a memory module
Prerequisites
1
Follow the safety guidelines listed in
2
Follow the procedure listed in
Before working inside your system
.
3
If applicable,
WARNING:
Allow the memory modules to cool after you power off the system. Handle the memory modules by the card edges
and avoid touching the components or metallic contacts on the memory module.
CAUTION:
To ensure proper system cooling, memory module blanks must be installed in any memory socket that is not occupied.
Remove memory module blanks only if you intend to install memory modules in those sockets.
64
Installing and removing system components