Dell PowerEdge R420 Technical Guide - Page 20
Memory RAS features, Feature, Description
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Memory RAS features Reliability, availability, serviceability (RAS) features help keep the system online and operational without significant impact to performance, and can decrease data loss and crashing due to errors. RAS aids in rapid, accurate diagnosis of faults that require service. Table 10 describes the RAS features supported on the R420. Table 10. Memory RAS features Feature Description Dense configuration optimized profile Memory demand and patrol scrubbing Recovery from single DRAM device failure Failed DIMM isolation Memory mirroring: intra-socket Memory address parity protection Memory sparing (rank) Memory thermal throttling Increased memory reliability can be a result from this selectable platform profile that adjusts parameters to reduce faults regarding refresh rates, speed, temperature and voltage Demand scrubbing is the ability to write corrected data back to the memory once a correctable error is detected on a read transaction. Patrol scrubbing proactively searches the system memory, repairing correctable errors. Recovery from Single DRAM Device Failure (SDDC) provides error checking and correction that protects against any single memory chip failure as well as multi- bit errors from any portion of a single memory chip. This feature provides the ability to identify a specific failing DIMM channel pair, thereby enabling the user to replace only the failed DIMM pair. Memory mirroring is a method of keeping a duplicate (secondary or mirrored) copy of the contents of memory as a redundant backup for use if the primary memory fails. The mirrored copy of the memory is stored in memory of the same processor socket. This feature provides the ability to detect transient errors on the address lines of the DDR channel. Memory sparing allocates one rank per channel as a spare. If excessive correctable errors occur in a rank or channel, it is moved to the spare area while the operating system is running to prevent the error from causing an uncorrectable failure. This feature helps to optimize power/performance and can also be used to prevent DIMMs from overheating. For information on memory mirroring and sparing configurations, see the Dell PowerEdge R420 Systems Owner's Manual on Support.Dell.com/Manuals. 20 PowerEdge R420 Technical Guide