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11 Memory Errors and Dell PowerEdge YX4X Server Memory RAS Features

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.

Memory Mirroring

Memory Mirroring Feature Support Table

DIMMs Supported

x4 DIMMs: 

x8 DIMMs: 

Memory Configuration

Required

• All identical DIMMs

• Memory channels must be populated as either all one DIMM per

channel or two DIMMs per channel

Memory Mirroring is a memory RAS feature available on Intel platforms that provides the highest level

of protection against memory errors – including uncorrectable errors – at the cost of a 50% memory

capacity reduction. This feature essentially works like RAID1 in the storage domain, where a redundant

copy of memory contents is stored in a separate memory location. If an uncorrectable error is detected

during a memory access at one location, then the mirrored content is retrieved instead. There is no

impact to overall memory performance when full mirroring is enabled except during heavy write traffic.

In order to configure for memory mirroring, all memory modules must be identical in size, speed,

density, and technology (RDIMM vs LRDIMM, etc). Additionally, memory channels must be populated

with all one DIMM or all two DIMMs (for example, 24 DIMM systems should have 12 DIMMs or 24

DIMMs installed). Memory mirroring is disabled by default and must be enabled through the BIOS setup

menu.

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

CPU