Dell R420xr owner manual Sample Memory Configurations, Memory Optimized Independent Channel Mode

NOTE: Advanced ECC with mirroring is not supported.

Memory Optimized (Independent Channel) Mode

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

Memory Sparing

NOTE: To use memory sparing, this feature must be enabled in the 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 system with three 8 GB dual-rank DIMMs, the available system memory is: 1/2 (ranks/channel) × 3 (DIMMs) × 8 GB = 12 GB, and not 3 (DIMMs) × 8 GB = 24 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 DIMM 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 DIMMs. In the event of an uncorrectable error, the system will switch over to the mirrored copy. This ensures SDDC and multi-bit protection.

Memory installation guidelines:

NOTE: The first memory channel for each processor (Channel 1) is disabled and not available for Memory Mirroring.

•Memory channels 2 and 3 must be populated.

•Memory modules 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 release tabs. For example, DIMMs installed in sockets A2 and A3 must be identical.

Sample Memory Configurations

The following tables show sample memory configurations that follow the appropriate memory guidelines stated in this section.

NOTE: 16 GB quad-rank RDIMMs are not supported.

NOTE: 1R, 2R, and 4R in the following tables indicate single-, dual-, and quad-rank DIMMs respectively.

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