Online-Spare Memory - IBM System x3650 Installation Manual

Configuration/Setup Utility program in the User's Guide on the IBM System x
Documentation CD for details about enabling memory mirroring.
When you use memory mirroring, you must install two pairs of DIMMs at a time.
The four DIMMs in each group must be identical. See Table 3 for the DIMM
connectors that are in each group.

Online-spare memory

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.
Online-spare memory reduces the amount of available memory. Before you can
enable this feature, you must install up to two additional pairs of DIMMs. The
online-spare DIMM pairs must be the same speed, type, and the same size as, or
larger than, the largest active DIMM pairs.
Enable online-spare memory through the Configuration/Setup Utility program. The
BIOS code assigns the online-spare DIMM pairs according to your DIMM
configuration. Online-sparing is enabled on a memory branch basis; the BIOS code
does not enable online-sparing on a branch that cannot support online-sparing. See
the illustration on page 13 for the memory branch structure. DIMM ranks are
online-spared if the DIMMs are installed according to the rules in Table 5 on page
17 or Table 6 on page 17.
Note: POST gives a warning message when online-sparing cannot be enabled on
both branches. However, no warning message is given when online-sparing is
enabled on one branch and disabled on the other.
Online-spare configurations are supported for each branch. See Table 5 on page 17
and Table 6 on page 17 for the online-spare DIMM connector assignments.
Important: Table 5 on page 17 shows the default DIMM online-spare scheme. If the
BIOS code level is version 1.04 or later, you can install the DIMMs according to the
scheme shown in Table 6 on page 17 instead.
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IBM System x3650 Type 7979: Installation Guide
Table 3. Memory mirroring DIMM installation sequence
Group DIMM connectors
1 1, 4, 7, and 10
2 2, 5, 8, and 11
3 3, 6, 9, and 12
Table 4. Memory mirroring DIMM functions
Group Active DIMMs
1 1, 4
2 2, 5
3 3, 6
Mirroring DIMMs
7, 10
8, 11
9, 12