Memory sparing
NOTE: To use memory sparing, this feature must be enabled in System Setup.
In this mode, one rank per channel is reserved as a spare. If persistent correctable errors are detected on a rank, the data from this
rank is copied to the spare rank, and the failed rank is disabled.
With 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 sixteen 4 GB single-rank memory modules, the available system memory is: 3/4
(ranks/channel) × 16 (memory modules) × 4 GB = 48 GB, and not 16 (memory modules) × 4 GB = 64 GB.
NOTE: Memory sparing does not offer protection against a multi-bit uncorrectable error.
NOTE: Both Advanced ECC/Lockstep and Optimizer modes support memory sparing.
Memory mirroring
Memory mirroring offers the strongest memory module reliability mode compared to all other modes, 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 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 installed in memory module sockets with white release levers must be identical and the same rule applies for
sockets with black and green release tabs. This ensures that identical memory modules are installed in matched pairs—for
example, A1 with A2, A3 with A4, A5 with A6, and so on.
Table 30. Processor configuration
Processor
Configuration
Memory population rules
Memory population information
Single CPU
Memory population order
{1,2}, {3,4}
See Memory mirroring note
Sample memory configurations
The following tables show sample memory configurations for two and four processor configurations that follow the appropriate
memory guidelines.
NOTE: 1R, 2R, 4R, and 8R in the following tables indicate single, dual, quad, and octal rank DIMMs.
Table 31. Memory configurations – two processors
System Capacity (in
GB)
DIMM Size (in GB) Number of
DIMMs
DIMM rank, organization,
and frequency
DIMM Slot Population
16
8
2
1R x8, 1866 MT/s
1R x8, 2133 MT/s
1R x8, 2400 MT/s
A1, B1
32
8
4
1R x8, 1866 MT/s
1R x8, 2133 MT/s
1R x8, 2400 MT/s
A1, A2, B1, B2
64
8
8
1R x8, 1866 MT/s
1R x8, 2133 MT/s
A1, A2, A3, A4, B1, B2, B3, B4
78
