Read Look-Ahead Caching for TLC Middle-Page Latency
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Solution Overview
Problem
The read time for multi-level cell (TLC) storage devices is significantly longer due to the higher latency of decoding middle pages, which can impact overall performance, especially during sustained workloads, and existing read look ahead (RLA) caching methods are inefficient with finite buffer capacity, leading to quality-of-service drops.
Innovation Solution
Implementing fluctuating RLA caching that dynamically manages an RLA buffer by caching latency-oriented pages in the buffer and non-latency-oriented pages in the memory device, optimizing buffer usage and balancing workload across sequential read ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If middle pages are used to store data in TLC memory devices, then storage capacity is improved, but read performance deteriorates due to higher decoding latency
Solution Approach 1:
The system performs preliminary actions by identifying latency-oriented pages (middle pages with high decoding latency) ahead of time and pre-caching their data in the RLA buffer during idle periods. This allows the system to prepare high-latency data in advance, so when read requests arrive, the data is already available in the buffer, eliminating the latency penalty during actual read operations.
2Adaptability or versatility
If RLA buffer capacity is allocated to multiple host read streams, then buffer utilization is improved, but sequential read performance deteriorates due to reduced buffer space per stream
Solution Approach 1:
The system performs preliminary identification of latency-oriented pages and pre-caches them in the RLA buffer during idle periods between host read requests. This advance preparation ensures that when multiple read streams arrive, the high-latency data is already cached and ready, allowing the system to maintain high sequential read performance even with limited buffer capacity shared across multiple streams.
Data Source
AI summary
A storage device manages a read look ahead (RLA) buffer with fluctuating RLA caching. The storage device includes a memory device to store data in a format including upper, middle, and lower pages and an RLA buffer to store data retrieved from the memory device. When a controller on the storage device receives a host read request, the controller predicts data to be included in a subsequent host read request. The controller then determines a set of pages storing the predicted data, identifies latency-oriented pages in the set of pages, retrieves data from the latency-oriented pages, and stores the data in the RLA buffer. When the storage device receives the subsequent host read request including the predicted data, the controller reads a first portion of the predicted data from the RLA buffer and a second portion of the predicted data from the memory device.