Dell PowerVault NX400, Owner'S Manual

Page: 42 / 123

Memory Optimized (Independent Channel) Mode
This mode supports SDDC only for memory modules that use x4 device width and does not impose any specific slot
population requirements.
Memory Sparing
NOTE: To use memory sparing, this feature must be enabled in the System Setup.
In this mode, one rank per channel is reserved as a spare. If persistent correctable errors are detected on a rank, the
data from this rank is copied to the spare rank and the failed rank is disabled.
With memory sparing enabled, the system memory available to the operating system is reduced by one rank per
channel. For example, in a system with three 8 GB dual-rank DIMMs, the available system memory is: 1/2 (ranks/
channel) × 3 (DIMMs) × 8 GB = 12 GB, and not 3 (DIMMs) × 8 GB = 24 GB.
NOTE: Memory sparing does not offer protection against a multi-bit uncorrectable error.
NOTE: Both Advanced ECC/Lockstep and Optimizer modes support Memory Sparing.
Memory Mirroring
Memory Mirroring offers the strongest DIMM reliability mode compared to all other modes, providing improved
uncorrectable multi-bit failure protection. In a mirrored configuration, the total available system memory is one half of
the total installed physical memory. Half of the installed memory is used to mirror the active DIMMs. In the event of an
uncorrectable error, the system will switch over to the mirrored copy. This ensures SDDC and multi-bit protection.
Memory installation guidelines:
• Memory sockets A1 and A4 are disabled and you can populate DIMMs in memory sockets A2, A3, A5, and A6.
• DIMMs installed in memory sockets with white release tabs must be identical and similar rule applies for
sockets with black release tabs. For example, DIMMs installed in sockets A1, A2, and A3 must be identical.
Sample Memory Configurations
The following table shows sample memory configurations that follow the appropriate memory guidelines stated in this
section.
NOTE: 16 GB quad-rank RDIMMs are not supported.
NOTE: 1R and 2R in the following table indicates single- and dual-rank DIMMs respectively.
Table 1. Memory Configurations
System Capacity (in
GB)
DIMM Size (in GB) Number of DIMMs DIMM Rank,
Organization, and
Frequency
DIMM Slot Population
2 2 1 1R, x8, 1333 MT/s, A1
1R, x8, 1600 MT/s
4 2 2 1R, x8, 1333 MT/s, A1, A2
1R, x8, 1600 MT/s
8 2 4 1R, x8, 1333 MT/s, A1, A2, A3, A4
1R, x8, 1600 MT/s
42