The Design and Implementation of a High-Performance Log-Structured RAID System for ZNS SSDs

2024-02-28

arXiv.org

AI Summary

To address the challenge of achieving high write parallelism while ensuring reliable and scalable striping management for Zone Append operations across multiple Zoned Namespace (ZNS) SSDs, this paper proposes ZapRAID—the first log-structured RAID system designed specifically for ZNS SSDs. Our approach introduces two key innovations: (1) a novel group-based data layout coupled with coarse-grained cross-group ordering, enabling lightweight per-group metadata management; and (2) a hybrid data management mechanism that jointly orchestrates Zone Write and Zone Append operations to exploit both intra-zone and inter-zone parallelism. Implemented atop a userspace block device framework leveraging native ZNS primitives, ZapRAID demonstrates substantial write throughput improvements in microbenchmarks, trace-driven workloads, and real-world applications—while maintaining efficient read performance, degraded-mode reads, crash recovery, and full-disk rebuild.

Technology Category

• Data Mining & Knowledge Management: Scalability, Parallel & Distributed Systems
• Search and Optimization: Distributed Search
• Multiagent Systems: Coordination and Collaboration

Application Category

• Systems and Infrastructure for Web, Mobile and WoT: Data management and stream processing for Web, mobile and wireless applications
• Responsible Web: Data and user privacy-enhancing technologies for the Web
• Security and Privacy: Large-scale security measurements

Abstract

Zoned Namespace (ZNS) defines a new abstraction for host software to flexibly manage storage in flash-based SSDs as append-only zones. It also provides a Zone Append primitive to further boost the write performance of ZNS SSDs by exploiting intra-zone parallelism. However, making Zone Append effective for reliable and scalable storage, in the form of a RAID array of multiple ZNS SSDs, is non-trivial since Zone Append offloads address management to ZNS SSDs and requires hosts to dedicatedly manage RAID stripes across multiple drives. We propose ZapRAID, a high-performance log-structured RAID system for ZNS SSDs by carefully exploiting Zone Append to achieve high write parallelism and lightweight stripe management. ZapRAID adopts a group-based data layout with a coarse-grained ordering across multiple groups of stripes, such that it can use small-size metadata for stripe management on a per-group basis under Zone Append. It further adopts hybrid data management to simultaneously achieve intra-zone and inter-zone parallelism through a careful combination of both Zone Write and Zone Append primitives. We implement ZapRAID as a user-space block device, and evaluate ZapRAID using microbenchmarks, trace-driven experiments, and real-application experiments. Our evaluation results show that ZapRAID achieves high write throughput and maintains high performance in normal reads, degraded reads, crash recovery, and full-drive recovery.

Problem

• Enhances write performance in ZNS SSDs.
• Manages RAID stripes across multiple drives effectively.
• Achieves intra-zone and inter-zone parallelism.

Innovation

• Group-based data layout for RAID
• Hybrid data management strategy
• User-space block device implementation