Memory rank sparing

The memory rank sparing feature disables the failed memory from the system configuration and activates a rank sparing DIMM to replace the failed active DIMM.

You can enable rank sparing memory in the Setup utility, select System Settings > Memory. For more information, see Using the Setup utility.

The maximum available memory is reduced when memory rank sparing mode is enabled.

The memory rank sparing mode requires an even number of DIMMs. If your server has an odd number of DIMMs installed, ensure that you disable the memory rank sparing mode from the Memory menu in Setup Utility. See Using the Setup utility.

Note

After disabling the memory rank sparing mode, if a message prompts that the memory configuration is not valid, restart the IMM2. Alternatively, you can turn off the server, disconnect it from and then reconnect it to ac power, and then turn on the server again.

The following diagram lists the DIMM connectors on each memory channel.

Figure 1. Connectors on each memory channel

Follow the installation sequence for rank sparing mode:

Install at least one quad-rank DIMM in a channel.
Install at least two single-rank or dual-rank DIMMs in a channel.

Table 1. Memory rank sparing mode DIMM population sequence when only quad-rank RDIMMs are installed
Number of installed microprocessor	DIMM connector population sequence on the system board
One	1, 4, 9, 12, 2, 5, 8, 11
Two	1, 13, 4, 16, 9, 21, 12, 24, 2, 14, 5, 17, 8, 20, 11, 23

Table 2. Memory rank sparing mode DIMM population sequence when single/dual/quad rank DIMMs are installed and the total number of DIMMs is even.
DIMMs	Number of installed microprocessor	DIMM connector population sequence on the system board
One Microprocessor
1st set	1	1, 2
2nd set	1	4, 5
3rd set	1	8, 9
4th set	1	11, 12
5th set	1	3, 6
6th set	1	7, 10
Two Microprocessors
1st set	2	1, 2
2nd set	2	13, 14
3rd set	2	4, 5
4th set	2	16, 17
5th set	2	8, 9
6th set	2	20, 21
7th set	2	11, 12
8th set	2	23, 24
9th set	2	3, 6
10th set	2	15, 18
11th set	2	7, 10
12th set	2	19, 22

Table 3. Memory rank sparing mode DIMM population sequence when single/dual/quad rank DIMMs are installed and the total number of DIMMs is odd.
DIMMs	Number of installed microprocessor	DIMM connector population sequence on the system board
One Microprocessor
1st set	1	1, 2, 3
2nd set	1	4, 5
3rd set	1	8, 9
4th set	1	11, 12
5th set	1	6, 7
Two Microprocessors
1st set	2	1, 2, 3
2nd set	2	13, 14
3rd set	2	4, 5
4th set	2	16, 17
5th set	2	8, 9
6th set	2	20, 21
7th set	2	11, 12
8th set	2	23, 24
9th set	2	6, 7
10th set	2	18, 19
11th set	2	10, 22

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