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In addition, to maintain the highest levels of system availability, when a memory
error is detected during POST or memory configuration, the server can
automatically disable the failing memory bank and continue operating with
reduced memory capacity. You can manually re-enable the memory bank after
the problem is corrected by using the Setup menu in the BIOS.
Memory ProteXion, memory mirroring, and Chipkill provide the memory
subsystem with multiple levels of redundancy. Combining Chipkill with Memory
ProteXion allows up to two memory chip failures for each memory port on the
x3850 M2 and x3950 M2, for a total of eight failures sustained.
The system takes the following sequence of steps regarding memory failure
detection and recovery:
1. The first failure detected by the Chipkill algorithm on each port does not
generate a light path diagnostics error because Memory ProteXion recovers
from the problem automatically.
2. Each memory port can sustain a second chip failure without shutting down.
3. Provided that memory mirroring is enabled, the third chip failure on that port
sends the alert and takes the DIMM offline, but keeps the system running out
of the redundant memory bank.
1.9 SAS controller and ports
The x3850 M2 and x3950 M2 have a disk subsystem comprised of an LSI Logic
1078 serial-attached SCSI (SAS) controller and four internal 2.5-inch SAS
hot-swap drive bays. The x3850 M2 and x3950 M2 support internal RAID-0 and
RAID-1. The optional ServeRAID MR10k provides additional RAID levels and a
256 MB battery-backed cache.
SAS is the logical evolution of SCSI. SAS uses much smaller interconnects than
SCSI, while offering SCSI compatibility, reliability, performance, and
manageability. In addition, SAS offers longer cabling distances, smaller form
factors, and greater addressability.
The x3850 M2 and x3950 M2 has an external SAS x4 port used in conjunction
with the optional ServeRAID MR10k. This external port supports SAS non-RAID
disk enclosures such as the EXP3000. This port has an SFF-8088 connector.
For more information about the onboard SAS controller and the ServeRAID
MR10k daughter card, see Figure 3-22 on page 131 in section 3.3.3,
"ServeRAID-MR10k RAID controller" on page 128.
42
Planning, Installing, and Managing the IBM System x3950 M2
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