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Mode-specific guidelines
The configurations allowed depend on the memory mode selected in the System BIOS.
Table 8. Memory operating modes
Memory Operating Mode
Optimizer Mode
Mirror Mode
Single Rank Spare Mode
Multi Rank Spare Mode
Dell Fault Resilient Mode
Optimizer Mode
This mode supports Single Device Data Correction (SDDC) only for memory modules that use x4 device width. It does not
impose any specific slot population requirements.
Description
The Optimizer Mode if enabled, the DRAM controllers
operate independently in the 64-bit mode and provide
optimized memory performance.
The Mirror Mode if enabled, the system maintains two
identical copies of data in memory, and 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. This feature provides maximum
reliability and enables the system to continue running even
during a catastrophic memory failure by switching over to
the mirrored copy. The installation guidelines to enable Mirror
Mode require that the memory modules be identical in size,
speed, and technology, and they must be populated in sets of
6 per processor.
Single Rank Spare Mode allocates one rank per channel
as a spare. If excessive correctable errors occur in a rank
or channel, while the operating system is running, they are
moved to the spare area to prevent errors from causing
an uncorrectable failure. Requires two or more ranks to be
populated in each channel.
Multi Rank Spare Mode allocates two ranks per channel
as a spare. If excessive correctable errors occur in a rank
or channel, while the operating system is running, they are
moved to the spare area to prevent errors from causing an
uncorrectable failure. Requires three or more ranks to be
populated in each 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 sixteen 16
GB single-rank memory modules, the available system memory
is: 3/4 (ranks/channel) × 16 (memory modules) × 16 GB =
192 GB, and not 16 (memory modules) × 16 GB = 256 GB.
For multi rank sparing, the multiplier changes to 1/2 (ranks/
channel).
NOTE:
To use memory sparing, this feature must be
enabled in the BIOS menu of System Setup.
NOTE:
Memory sparing does not offer protection against
a multi-bit uncorrectable error.
The Dell Fault Resilient Mode if enabled, the BIOS creates
an area of memory that is fault resilient. This mode can be
used by an OS that supports the feature to load critical
applications or enables the OS kernel to maximize system
availability.
Installing and removing system components
35
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