SSD Page Grouping by Overwrite Count to Cut GC Latency
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Solution Overview
Problem
Existing data placement technologies in Solid State Drives (SSDs) face challenges in generating accurate longevity hints for data segregation, leading to inefficiencies in Write Amplification Factor (WAF) and latency due to Garbage Collection (GC) processes.
Innovation Solution
The storage device analyzes the overwrite count of data placement by the host system and adjusts it to match the average overwrite count within the SSD, grouping pages accordingly and updating a log page to record these changes, while the host system generates a probability matrix based on data attributes to improve data placement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the host system sends longevity hints for data placement, then data segregation can be performed to minimize WAF and latency, but the correctness of the hint cannot be guaranteed and effective hint generation from the host system remains challenging
Solution Approach 1:
The storage device monitors actual data access patterns and overwrite counts, then feeds this information back to adjust the placement handles. The system compares expected longevity (from hints) with actual longevity (from monitoring) and uses this feedback to correct placement decisions, ensuring data is placed according to actual usage patterns rather than relying solely on potentially incorrect host-generated hints.
Solution Approach 2:
The storage device autonomously monitors its own data access patterns, overwrite counts, and garbage collection behavior to generate corrected longevity hints. Instead of relying entirely on the host system to generate accurate hints, the storage device uses its internal monitoring capabilities to self-correct and optimize data placement independently.
2Productivity
If data placement technologies use longevity hints for segregation, then Write Amplification Factor can be minimized, but latency due to Garbage Collection processes increases
Solution Approach 1:
The storage device performs preliminary monitoring and analysis of data access patterns and overwrite counts before finalizing data placement. By pre-identifying data with similar longevity characteristics and pre-grouping them into appropriate placement handles, the system reduces the need for subsequent garbage collection operations and minimizes GC-induced latency.
Solution Approach 2:
The system creates separate placement handles with distinct characteristics based on local data properties (overwrite count, access patterns). Each placement handle is optimized for specific longevity requirements, allowing targeted garbage collection that minimizes overall latency by processing only the necessary data in each handle rather than scanning the entire storage device.
3Measurement precision
If the storage device monitors and adjusts data placement based on overwrite counts, then data placement accuracy improves, but device complexity increases
Solution Approach 1:
The storage device's existing monitoring infrastructure is leveraged to serve multiple purposes: tracking data access patterns, counting overwrites, monitoring garbage collection behavior, and generating placement corrections. By making the monitoring system multi-functional, the patent avoids adding separate dedicated hardware or software components, thereby limiting the increase in device complexity while achieving improved placement accuracy.
Data Source
AI summary
The present disclosure provides methods include receiving an I-O from host system, determining whether an overwrite count of data of the I-O placed by the host system in a placement handle is different from an average overwrite count of data in the placement handle upon receiving the I-O, grouping one or more pages corresponding to the data of the I-O in the placement handle to another placement handle that matches the overwrite count of the data of the I-O based on the determination of the overwrite count of the data of the I-O in the placement handle being different from the average overwrite count of data in the placement handle of the storage device during an internal operation, and. updating a log page to record the grouping of the one or more pages.