Storage Controller ZRWA Status Tracking for NVMe Reliability
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Solution Overview
Problem
Non-volatile memory devices experience frequent garbage collection due to random access, leading to a decrease in storage device lifetime, and require random write operations which can be inefficient and unreliable, especially in zone regions where data sequentiality is maintained.
Innovation Solution
A storage controller that manages zone regions using a zoned namespace (ZNS) standard, allowing for random write operations within a zone random write area (ZRWA) and implicit ZRWA flush region (IZFR), with status information management to ensure accurate data storage and retrieval, preventing data loss during power interruptions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If random access is used in non-volatile memory devices, then data storage flexibility is improved, but garbage collection frequency increases and device lifetime decreases
Solution Approach 1:
The storage device is divided into multiple zone regions (sequential write zone, random write zone, read-only zone) with different access characteristics. This segmentation allows the system to maintain both sequential access efficiency for extended lifetime and random access capability where needed, resolving the contradiction between storage flexibility and device lifetime.
2Adaptability or versatility
If random write operations are performed in zone regions, then data storage flexibility is improved, but data reliability decreases
Solution Approach 1:
Different zone regions are assigned different quality characteristics: the sequential write zone maintains strict sequentiality for reliability, while the random write zone allows flexible random access. This local differentiation resolves the contradiction by providing random write capability only where it doesn't compromise overall data reliability.
Solution Approach 2:
The zone regions can be dynamically created, extended, or converted between different access modes based on workload requirements. This dynamic adjustment allows the system to optimize between sequential and random access characteristics over time, maintaining both flexibility and reliability.
3Device complexity
If zone regions are managed without status information tracking, then device complexity is reduced, but data loss risk increases during power interruptions
Solution Approach 1:
The storage controller maintains status information in a zone status table that preliminarily tracks the state of each zone region (sequential write, random write, read-only) and the host's perceived zone boundaries. This preliminary tracking prevents data loss during power interruptions without requiring complex real-time synchronization mechanisms.
Solution Approach 2:
The zone status table acts as an intermediary structure that stores metadata about zone regions, including the last perceived zone boundary from the host and the current zone state. This intermediary allows the system to recover consistent state information after power interruptions without complex communication protocols.
Data Source
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AI summary
A method of operating a storage controller which communicates with a host device and a non-volatile memory device is provided. The method includes: receiving a first command from the host device indicating a read operation of first status information of a first zone random write area (ZRWA) in a first zone region, wherein the first command complies with a zoned namespace (ZNS) standard; obtaining the first status information from a zone status table in the storage controller based on the first command, wherein the first status information indicates at least a portion of a first physical region of the non-volatile memory device corresponding to the first ZRWA in which first data are stored; and providing the first status information to the host device.