
Dell EMC PowerEdge M640 Installation and Service Manual
Memory sparing
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 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.