Release Notes

10 Memory Errors and Dell PowerEdge YX4X Server Memory RAS Features
CPU
DIMM A8
DIMM A2
DIMM A7
DIMM A1
DIMM A9
DIMM A3
DIMM A5
DIMM A11
DIMM A4
DIMM A10
DIMM A6
DIMM A12
Four
Physical
Ranks
Spare Rank
Figure 5 - Example of two 16GB (2Rx8) RDIMMs with one rank held as spare
In order to support single rank sparing, a system must be populated with at least two memory ranks per
memory channel. The memory capacity reduction due to rank sparing is based on the memory
configuration (number of ranks per channel and size of ranks). After one failover event has occurred, no
further failover can occur in single rank sparing mode.
• Rank per channel capacity reduction impact (assuming same sized ranks) = 1 per number of ranks
o E.g. 4 ranks = 25% reduction
• Largest rank in channel is always held as spare
o E.g. One 32 GB RDIMM (2Rx4) and one 16 GB RDIMM (2Rx8) installed = two 16 GB ranks and
two 8 GB ranks. One of the 16 GB ranks will be held as spare, resulting in a 33% capacity
reduction.
In order to support multi rank sparing, a system must be populated with at least three memory ranks
per memory channel. Like single rank sparing, the memory capacity reduction due to rank sparing is
based on the memory configuration (number of ranks per channel and size of ranks). Up to two failover
events may occur in multi rank sparing mode.
• Rank per channel capacity reduction impact (assuming same sized ranks) = 2 per number of ranks
o E.g. 4 ranks = 50% reduction
• Largest rank in channel is always held as spare
o E.g. One 32 GB RDIMM (2Rx4) and one 16 GB RDIMM (2Rx8) installed = two 16 GB ranks and
two 8 GB ranks. Both 16 GB ranks will be held as spares, resulting in a 66% capacity
reduction.