Memory mirroring
You can configure the server to use memory mirroring. Memory mirroring stores
data in a pair of DIMMs simultaneously. If a failure occurs, the memory controller
switches from the active DIMM to the mirroring DIMM. Memory mirroring reduces
the amount of available memory. Enable memory mirroring through the server
firmware (see “Configuring the server” on page 253 for details about enabling
memory mirroring.
When you use memory mirroring, you must install a pair of DIMMs at a time. One
DIMM must be in channel 0, and the mirroring DIMM must be in the same slot in
channel 1. The two DIMMs in each pair must be identical in size, type, rank (single,
dual, or quad), and organization, but not in speed. The channels run at the speed of
the slowest DIMM in any of the channels. See Table 17 and Table 18 for the DIMM
connectors that are in each pair.
Table 17. Microprocessor 1 memory-mirroring DIMM installation sequence
Microprocessor
number Pair DIMM connectors
1 1 3, 6
1 2 2, 5
1 3 1, 4
Table 18. Microprocessor 2 memory-mirroring DIMM installation sequence
Microprocessor
number Pair DIMM connectors
2 1 15, 12
2 2 14, 11
2 3 13, 10
Note that you can install DIMMs for microprocessor 2 as soon as microprocessor 2
is installed; you are not required to fill all the DIMM connectors for microprocessor 1
first.
Online-spare memory
The server supports online-spare memory. This feature disables the failed memory
from the system configuration and activates an online-spare DIMM to replace the
failed active DIMM. You can enable either online-spare memory or memory
mirroring in the Setup utility (see “Using the Setup utility” on page 255). When you
use the memory online-spare feature, consider the following information:
v The memory online-spare feature is supported on server models with an Intel
Xeon
™
5600 series microprocessor.
v When you enable the memory online-spare feature, you must install three DIMMs
per microprocessor at a time. The first DIMM must be in channel 0, the second
DIMM in channel 1, and the online-spare DIMM in channel 2. The DIMMs must
be identical in size, type, rank, and organization, but not in speed. The channels
run at the speed of the slowest DIMM in any of the channels.
v The maximum available memory is reduced to 2/3 of the installed memory when
memory online-spare mode is enabled. For example, if you install 72 GB of
memory using RDIMMs, only 48 GB of addressable memory is available when
you use memory online-spare.
Chapter 5. Removing and replacing server components 221
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