PDL Abstract

RAIZN: Redundant Array of Independent Zoned Namespaces

ASPLOS ’23, March 25–29, 2023, Vancouver, BC, Canada. Supercedes Carnegie Mellon University Parallel Data Lab Technical Report CMU-PDL-22-101, January 2022.

Thomas Kim, Jekyeom Jeon, Nikhil Arora, Huaicheng Li, Michael Kaminsky, David G. Andersen, Gregory R. Ganger, George Amvrosiadis, Matias Bjørling*

Carnegie Mellon University
* Western Digital Corporation

Zoned Namespace (ZNS) SSDs are the latest evolution of hostmanaged flash storage, enabling improved performance at a lower cost-per-byte than traditional block interface (conventional) SSDs. To date, there is no support for arranging these new devices in arrays that offer increased throughput and reliability (RAID). We identify key challenges in designing redundant ZNS SSD arrays, such as managing metadata updates and persisting partial stripe writes in the absence of overwrite support from the device.

We present RAIZN, a logical volume manager that exposes a ZNS interface and stripes data and parity across ZNS SSDs. RAIZN provides more stable throughput and lower tail latencies than an mdraid array of conventional SSDs based on the same hardware platform. RAIZN achieves superior performance because devicelevel garbage collection slows down conventional SSDs.We confirm that the benefits of RAIZN translate to higher layers by adapting the F2FS file system, RocksDB key-value store, and MySQL database to work with ZNS and leverage its benefits by closely controlling garbage collection. Compared to arrays of conventional SSDs experiencing on-device garbage collection, RAIZN leverages the ZNS interface to maintain consistent performance with up to 14× higher throughput and lower tail latency.

KEYWORDS: Zoned namespaces, storage, RAID, reliability

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