Lenovo 6241, Installation And Service Manual

Page: 73 / 1990

Memory rank sparing in lockstep mode
This information covers using the memory rank sparing feature of the lockstep memory mode.
The server supports memory rank sparing. Memory rank sparing reserves memory capacity for failover in the
event of a DIMM failure, and the reserved capacity is subtracted from the total available memory. Memory
sparing provides less redundancy than memory mirroring does. If a predetermined threshold of correctable
errors is reached, the contents of the failing DIMM are copied to the spare memory, and the failing DIMM or
rank is disabled.
To enable memory sparing through the Setup utility, select System Settings → Memory → Memory Mode .
For more information, see “Using the Setup utility” on page 123. For more information and notes about
installing DIMMs, see “Installing a memory module” on page 46.
The DIMM installation order for memory rank sparing follows the independent mode (performance) or
lockstep mode (RAS) installation order based on the mode of operation selected. For more information, see
“Independent memory mode” on page 53, and “Lockstep memory mode” on page 57.
Consider the following when using the memory rank sparing feature in independent memory mode:
• Memory rank sparing is not supported if memory mirroring is enabled.
• The spare rank must have identical or larger memory capacity than all the other ranks on the same DDR3
or DDR4 channel.
• When single-rank DIMMs (that is, 4 GB and 8 GB) are used, a minimum of two rank DIMMs must be
installed per memory channel to support memory sparing.
• When multi-rank DIMMs (that is, 16 GB, 32 GB, and 64 GB) are used, one multi-rank DIMM can be
installed per memory channel to support memory sparing.
• The total memory available in the system is reduced by the amount of memory allocated for the spare
ranks.
DIMM installation instructions
This information provides instructions on how to install DIMMs for memory-mirroring mode.
Notes:
• The information and installation procedures in this documentation apply to both the 4-socket and the 8-
socket configurations of the server, unless otherwise specified. Most of the illustrations in the
documentation show the 4-socket configuration of the server.
• For additional information and notes that you need to consider when installing DIMMs, see “Installing a
memory module” on page 46 and “eXFlash DIMMs” on page 50.
Attention: Static electricity that is released to internal server components when the server is powered on
might cause the server to stop, which might result in the loss of data. To avoid this potential problem, always
use an electrostatic-discharge wrist strap and plug it into the electrostatic-discharge connector on the front
of the server (see “Front view of the server” on page 24 for the location of this connector) or other grounding
system when you work inside the server with the power on.
The following illustration shows the DIMM connectors on the microprocessor side of the compute book
board.
Chapter 2
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Installing optional devices
59