Lenovo RD120 - ThinkServer - 6447 User Manual page 75

v Each DIMM in a pair must be the same size, speed, type, and technology to
ensure that the server will operate correctly.
v You 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.
v The 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.
v You 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.
v When 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.
DIMM 12
Channel 3
DIMM 11
DIMM 10
Branch 1
DIMM 9
DIMM 8
Channel 2
DIMM 7
DIMM 6
Channel 1
DIMM 5
DIMM 4
Branch 0
DIMM 3
Channel 0
DIMM 2
DIMM 1
Chapter 2. Installing optional devices
61