Concept Guide

9 Memory Errors and Dell PowerEdge YX4X Server Memory RAS Features
in the BIOS setup under the power management menu. Memory patrol scrub may have an impact on
system performance for some workloads while it is running.
FYI: Demand Scrub occurs when the memory controller encounters a correctable
error during a regular run-time read transaction and writes back corrected data.
The usefulness of Patrol Scrub is highlighted in scenarios where memory access
patterns are highly focused in some areas and thus the other areas are not getting
the benefits of Demand Scrub.
Memory Page Retire (MPR)
Memory Page Retire Feature Support Table
DIMMs Supported
x4 DIMMs: 
x8 DIMMs: 
Memory Page Retire (MPR) is a feature implemented by PowerEdge server BIOS that instructs operating
systems to stop using memory page locations (4 KB in size) that BIOS has deemed as potentially
unhealthy – essentially removing it from the operating system’s memory pool. This feature is also known
as Operating System Memory Page Retirement or Page Off-lining. BIOS makes the determination of a
potentially unhealthy memory page based on a proprietary PowerEdge server algorithm that takes into
account correctable error patterns and error rates at a given memory page location.
Studies into memory page retirement (aka off-lining) have found that MPR can reduce memory error
rates by as much as 94% [5]. This feature is automatically enabled in BIOS and will be activated provided
the operating system supports memory page retirement. Most modern operating systems support the
capability of receiving such memory page retirement requests. To know more about compatibility of OSs
with receiving such request, contact your OS vendor.
Memory Rank Sparing
Memory Rank Sparing Feature Support Table
DIMMs Supported
x4 DIMMs: 
x8 DIMMs: 
Memory Configuration
Required
• Single Rank Sparing – Two or more memory ranks per memory
channel
• Multi Rank Sparing – Three or more memory ranks per memory
channel
Memory Rank Sparing is a memory RAS feature available on Intel platforms that will reserve one or
more memory ranks per channel as spares for failover. When the PowerEdge server memory health
monitor has determined that one of the ranks in a memory channel has degraded, it will trigger rank
sparing failover. The failover process consists of checking the health of the spare rank(s) through patrol