Advanced Ecc (Lockstep); Memory Optimized (Independent Channel) Mode; Memory Sparing; Memory Mirroring - Dell PowerEdge R930 Owner's Manual

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NOTE: You can mix x4 and x8 DRAM based DIMMs to support RAS features. However, all guidelines
for specific RAS features must be followed. x4 DRAM based DIMMs retain Single Device Data
Correction (SDDC) in memory optimized (independent channel) mode. x8 DRAM based DIMMs
require Advanced ECC mode to gain SDDC.
The following sections provide additional slot population guidelines for each mode:

Advanced ECC (Lockstep)

Advanced ECC mode extends SDDC from x4 DRAM based DIMMs to both x4 and x8 DRAMs. This
protects against single DRAM chip failures during normal operation.
Memory installation guidelines:
Memory modules within each matched pair must be identical in size, speed, and technology.
DIMMs installed in memory sockets with white release tabs must be identical and similar rule applies
for sockets with black and green release tabs. This ensures that identical DIMMs are installed in
matched pairs - for example, A1 with A3, A2 with A4, A5 with A7, and so on.
NOTE: Advanced ECC with Mirroring is supported.

Memory optimized (independent channel) mode

This mode supports SDDC only for memory modules that use x4 device width, and this mode does not
impose any specific slot population requirements.

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 8 GB dual-rank memory
modules, the available system memory is: 3/4 (ranks/channel) × 16 (memory modules) × 8 GB = 96 GB,
and not 16 (memory modules) × 8 GB = 128 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
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