Using Memory Ras Features - NEC Express5800/R120d-2E User Manual

Chapter 2 Preparations

1.10.7 Using Memory RAS Features

The server has RAS feature including "Standard (independent) memory feature (x4 SDDC ECC memory)",
"Memory mirroring feature", "Memory LockStep feature (x8 SDDC ECC memory)", and Memory Sparing
feature. SDDC (Single Device Data Correction) allows automatic correction of memory error (multi-bit
error).
The memory area on the motherboard of the server is divided into three memory channels as shown in the
figure below.
The memory mirroring and LockStep features keep memory redundancy between memory two channels by
monitoring or altering memory active/inactive status, respectively.
(1) Memory Mirroring Feature
The memory mirroring feature writes the same data into two groups of DIMMs corresponding with each other
between memory channels (channels 2 and 3) to provide data redundancy.
The memory mirroring feature can be used under the following conditions:
• Install DIMMs in two DIMM sockets configuring a mirror set.
• All the installed DIMMs should have the same capacity.
• Run SETUP (refer to Chapter 2 (1. System BIOS) in "Maintenance Guide"), change parameters
appropriately in the [Mirror] menu selected as shown below, save the settings and exit from SETUP.
[Advanced] – [Memory Configuration] – [Memory RAS Mode] – [Mirror]
Run SETUP again, and check if the status of additionally installed DIMMs shows "Mirror".
• Installation order depends on CPU configuration. See the figure below.
The mirroring cannot be configured in the following case:
• Memory mirroring within a specific memory channel
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• To use the Memory Mirroring feature or Memory LockStep (x8 SDDC ECC memory)
Note
feature, additional memory board (N8102-493/494/495/496) is required.
• To use the Memory Sparing feature, additional memory board (N8102-497/498) is
required.
• To use Standard (Independent) memory feature (x4 SDDC), additional memory board
(N8102-489/490/491/492) is required.
• The memory mirroring feature uses channels 2 and 3. In memory mirroring
Important
configuration, the memory channel 1 of each CPU (CPU1-DIMM1/4,
CPU2-DIMM1/4) is disabled.
• To use the Memory Mirroring feature, additional memory board
(N8102-493/494/495/496), equipped with two DIMMs of same model, is required.
Tips
The operating system only recognizes a half of the total physical capacity.
Express5800/R120d-2E User's Guide
1. Installing Internal Optional Devices