Patrol Scrub and RAS Policy: Review Checklist

Review checklist

Review Checklist for Patrol Scrub and RAS Policy focuses on scrub interval coverage, latent fault dwell time, corrected-before-failure ratio. The purpose is to turn memory observations into mechanism-backed actions with explicit owners and release-safe validation.

• Workload scope and SLA targets are explicit.

• Environment tags are locked and reproducible.

• First failing transition is proven by command-level evidence.

• Owner and rollback criteria are documented.

• Validation matrix covers performance, stability, and reliability.

• Owners signed: firmware owner, system architect, SRE / fleet reliability owner.

DRAM deep dive

Reliability closure combines ECC policy, scrub cadence, and disturbance mitigation like row-hammer controls.

Concept diagram

RELIABILITY LOOP

error detect -> ECC correct/report -> scrub/retire policy -> monitor recurrence

Metric graph

ERROR MANAGEMENT TREND

correctable events    ███████
silent-data-risk      ██
unrecoverable events  █

Reports and artifacts

• correctable/uncorrectable error trend

• scrub interval effectiveness report

• row-hammer monitor log

• fault-injection coverage summary

Mini case study

Relaxed scrub interval improved bandwidth in test but allowed burst correctables to cluster into service-visible latency spikes.

Debug branches

• Segment ECC events by bank, rank, and temperature

• Tune scrub cadence with workload-aware idle windows

• Verify row-hammer mitigation using adversarial patterns

Senior review question

Ask: which latency, bandwidth, and reliability evidence proves this DRAM topic is closed under real traffic?

Key takeaways

• Always tie controller and PHY counter shifts to application latency and throughput outcomes.

• Lock firmware timing profile, thermal condition, and DIMM state before comparing DRAM captures.

Common pitfalls

• Chasing peak bandwidth while ignoring p99 latency and fairness tails.

• Changing timing guardbands without separating SI noise from scheduling issues.

• Declaring closure without reliability gates, fault injection, and regression replay.

Review checklist explanation

A checklist here protects against false closure. Every item should map to a known memory failure mode.

For Patrol Scrub and RAS Policy, minimum checklist: workload scope, scrub interval coverage, latent fault dwell time, corrected-before-failure ratio, artifact evidence (scrub scheduler log, CE aging report, patrol coverage audit), bottleneck class, owner, rollback path, and corner-matrix validation.

If controller or firmware changed, include fairness and RAS checks. If PHY or package assumptions changed, include SI/PI and thermal guardband evidence.