Concept Guide

15 Memory Errors and Dell PowerEdge YX4X Server Memory RAS Features
• If the impacted data was in user/application/VM memory, then the OS will terminate the
associated process or VM without impacting the rest of the system.
• If the impacted data was in user/application/VM memory but the OS had a redundant copy of
the data, then the associated process or VM will recover.
Consult your operating system documentation on error containment for more information on OS
behaviors.
Other Memory RAS Capabilities on PowerEdge servers
• Memory Map Out – If critical failures (such as uncorrectable errors) are detected in the memory
training and test phase of POST, PowerEdge servers will automatically map out the affected
DIMMs from the system memory pool. This prevents the faulty DIMM from incurring potential
service outages. The affected DIMM will not be mapped back into the memory pool until there
is a memory configuration change (such as a DIMM replacement).
Achieving Maximum Memory Up Time
Based on the memory RAS features discussed in the previous section, the following is a summary of how
users can configure their systems to achieve maximum memory up time:
• Configure server using genuine Dell DIMMs
o Benefit: Memory modules are fully validated and assured by Dell; additional self-healing
(PPR) resources above and beyond industry standards
• Configure server with x4 DRAM based DIMMs
o Benefit: Single DRAM Device Correction and ADDDC
• Configure server to operate in the following redundancy modes (in descending order of
protection):
o Best – Configure server to operate in Memory Mirroring Mode
▪ Benefit: RAID1 level memory protection, significantly reduced probability of
UCEs
▪ Downside: 50% memory capacity reduction
o Better – Configure server to operate in Fault Resilient Memory mode
▪ Benefit: Significantly reduced probability of UCEs in critical portions of memory
used by operating systems; low memory capacity reduction overhead
(depending on the system settings)
▪ Downside: Up to 25% memory capacity reduction, only officially supported
VMware vSphere 5.5 or higher only
o Good – Configure server to operate in Rank Sparing Mode
▪ Benefit: Run-time elimination of memory ranks that are operating in a degraded
state due to a large number of correctable errors
▪ Downside: Varying amount of memory capacity reduction depending on
memory configuration
• Configure server to run memory patrol scrub in ‘Extended Mode’