Memory sparing

After an error threshold is surpassed in a system protected by memory sparing, the content of a failing rank of DIMMs is copied to the spare rank. The failing rank is then taken offline and the spare rank placed online for use as active memory in place of the failed rank. Since the failover process involves copying of memory content, the level of memory redundancy provided by memory sparing is less than that provided by memory mirroring: memory mirroring is the preferred failure-protection choice for critical applications.

Figure 1. Processor and memory module layout

Table 1. Processor and memory module layout

1 DIMM 25 – 30	6 Processor socket 2
2 Processor socket 3	7 DIMM 19 – 24
3 DIMM 1 – 6	8 Processor socket 4
4 Processor socket 1	9 DIMM 43 – 48
5 DIMM 7 – 18	10 DIMM 31 – 42

Table 2. Channel and slot information of DIMMs around processor 1 and 2

Memory controllers		Controller 0						Controller 1
Channels		Channel 2		Channel 1		Channel 0		Channel 0		Channel 1		Channel 2
Slots		0	1	0	1	0	1	1	0	1	0	1	0
DIMM numbers (processor 1)		1	2	3	4	5	6	7	8	9	10	11	12
DIMM numbers (processor 2)		13	14	15	16	17	18	19	20	21	22	23	24

Table 3. Channel and slot information of DIMMs around processor 3 and 4

Memory controllers		Controller 1						Controller 0
Channels		Channel 2		Channel 1		Channel 0		Channel 0		Channel 1		Channel 2
Slots		0	1	0	1	0	1	1	0	1	0	1	0
DIMM numbers (processor 3)		25	26	27	28	29	30	31	32	33	34	35	36
DIMM numbers (processor 4)		37	38	39	40	41	42	43	44	45	46	47	48