Lenovo RD120 manual Dimm

DIMM 12	Channel 3
DIMM 11
DIMM 10
	Branch 1

DIMM 9
DIMM 8	Channel 2
DIMM 7
DIMM 6
DIMM 5	Channel 1
DIMM 4	Branch 0
DIMM 3
	Channel 0
DIMM 2
DIMM 1

vEach DIMM in a pair must be the same size, speed, type, and technology to ensure that the server will operate correctly.

vYou can configure the server to use memory mirroring. Memory mirroring stores data in two pairs of DIMMs simultaneously. If a failure occurs, the memory controller switches from the active pair to the mirroring pair. See “Memory mirroring” on page 62 for more information about memory mirroring and the DIMM installation sequence that is required.

vThe server supports online-spare memory. This feature disables the failed memory from the system configuration and activates an online-spare pair of DIMMs to replace the failed active DIMM pair. See “Online-spare memory” on page 63 for more information about online-spare memory and the DIMM configuration that is required.

vYou can enable either online-spare memory or memory mirroring, but not both at the same time. Online-spare memory provides more memory capacity than mirroring. Mirroring provides better memory protection but less memory capacity than online-spare memory.

vWhen you install or remove DIMMs, the server configuration information changes. When you restart the server, the system displays a message that indicates that the memory configuration has changed.

Note: When 4 GB or more of memory (physical or logical) is installed, some memory is reserved for various system resources and is unavailable to the operating system. The amount of memory that is reserved for system resources depends on the operating system, the configuration of the server, and the configured PCI options.

Chapter 2. Installing optional devices 61