Targeted Read Scrub for Storage Systems During Intensive Host Reads
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Solution Overview
Problem
Data stored in memory cells of a storage system can become corrupted by read, program, and erase operations, leading to errors that conventional periodic read scrub operations may disrupt intensive host read performance, particularly during prolonged gaming or high-read-throughput applications.
Innovation Solution
A targeted read scrub operation is performed by the controller, which determines if the system is in intensive-host-read mode and conducts specific scans such as periodic, random, or passive read scans to minimize disruption, reallocating pages with high bit error rates to new blocks while maintaining high read performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional periodic read scrub operations are performed, then bit error rates are controlled, but host read performance is disrupted during intensive read operations
Solution Approach 1:
The read scrub operation dynamically adjusts its behavior based on system state. The controller monitors whether the system is in intensive-host-read mode and modifies the read scrub operation accordingly - performing targeted scans only on portions of memory not currently being intensively read, rather than executing full periodic scans. This dynamic adaptation resolves the contradiction by making the error correction process flexible rather than rigid.
Solution Approach 2:
Instead of applying uniform read scrub operations across all memory, the system applies targeted read scrub operations only to specific portions of memory that are not currently being intensively accessed. This local approach concentrates error correction resources where they are most needed while leaving high-performance read operations undisturbed, thus maintaining both reliability and productivity.
2Productivity
If targeted read scrub operations are performed during intensive host reads, then host read performance is maintained, but bit error rates may increase in unscrubbed portions of memory
Solution Approach 1:
The targeted read scrub operation ensures continuous error correction coverage by systematically working through different portions of memory over time. Even though any single scrub operation covers only a portion of memory, the controller continuously monitors and re-scans memory regions, ensuring that all data eventually receives error correction treatment while maintaining uninterrupted host read performance throughout the process.
3Reliability
If full periodic read scrub operations are executed, then all memory is scanned for errors, but operational overhead increases and disrupts gaming or high-throughput applications
Solution Approach 1:
The system performs partial read scrub operations during intensive host read periods, scanning only the portions of memory not currently being accessed. This partial action is sufficient to maintain error correction coverage without the excessive overhead of full periodic scans, thus reducing time loss while still providing meaningful error detection and correction.
Data Source
AI summary
A storage system determines that it is undergoing intensive reads by a host, which can occur, for example, when the storage system is being used to play a video game for a prolonged period of time. As performing a conventional read scrub operation in that situation can result in a decrease in performance, the storage system can instead use a targeted read scrub operation to reduce the impact on host read performance. The targeted read scrub operation can take the form, for example, of a periodic read scan on areas of the memory that are not part of the intensive host read, random read scans on neighboring wordlines where only a single state is read, and/or a passive read scan where acceptable but risky pages are marked for relocation.