Zone Write Groups for ZNS SSD Data Recovery and Parity
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Solution Overview
Problem
Zoned NameSpace (ZNS) SSDs face challenges in implementing full zone failure protection due to erase unit size mismatches, leading to space loss for overprovisioning and limited system parallelism, and existing garbage collection processes are inefficient.
Innovation Solution
Implementing Zone Write Groups (ZWGs) that combine host zones with parity zones to assist in data recovery and parity accumulation, reducing the need for garbage collection by leveraging host device invalidation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ZNS zone capacity matches the size of an erase unit, then zone failure protection can be implemented, but significant space is lost for overprovisioning
Solution Approach 1:
The patent divides the storage space into ZNS zones and further segments protection mechanisms by introducing ZWG at the controller level. Instead of protecting at the individual zone level (which wastes space), it groups zones into ZWGs and protects at the group level, reducing redundant protection overhead while maintaining reliability.
Solution Approach 2:
The ZWG structure serves multiple functions simultaneously: it provides data protection through parity zones, enables efficient garbage collection by grouping zones with similar lifespan, and reduces overprovisioning space requirements. This multi-functionality resolves the contradiction by achieving protection without dedicated sacrifice space.
2Reliability
If ZNS zone capacity is increased to match the size of multiple erase units, then system parallelism is limited and overhead increases
Solution Approach 1:
Instead of using large zones that limit parallelism, the patent segments storage into smaller ZNS zones organized into ZWGs. This segmentation allows finer-grained parallel operations while maintaining protection capabilities through the ZWG structure, reducing the overhead associated with large zone management.
Solution Approach 2:
The patent introduces a new organizational dimension (ZWG grouping) above the zone level. This additional layer of organization allows efficient management of multiple small zones without the overhead of managing individual zones separately, resolving the complexity issue while maintaining protection.
3Productivity
If traditional garbage collection processes are used in ZNS SSDs, then data recovery efficiency is reduced and performance is impacted
Solution Approach 1:
The patent implements preliminary data protection by maintaining parity zones within ZWGs before data loss occurs. This preliminary action enables rapid data recovery without needing time-consuming garbage collection processes, as the recovery data is already prepared and stored in the parity zones.
Solution Approach 2:
The patent creates copies of data in parity zones within each ZWG. These copies serve as immediate recovery sources, eliminating the need for complex garbage collection processes to retrieve lost data, thereby improving recovery efficiency and reducing time loss.
Data Source
AI summary
Zone Write Groups (ZWGs) to assist data storage devices and host devices with data recovery. In one embodiment, a data storage device includes a memory storing a Zoned NameSpace (ZNS). The ZNS includes a ZWG including host zones and parity zones. An interface connects the data storage device with a host device. The data storage device includes a data storage device controller including an electronic processor and a memory. The data storage device controller populates the ZWG with buffers received from the host device. The data storage device controller detects corrupted data associated with the ZNS and requests one or more buffers stored in the ZWG. Once the data storage device controller receives the one or more buffers from the ZWG, the data storage device controller performs a recovery event with the one or more buffers.