ZNS+: Advanced zoned namespace interface for supporting in-storage zone compaction
- Authors
- Han, K.[Han, K.]; Gwak, H.[Gwak, H.]; Shin, D.[Shin, D.]; Hwang, J.-Y.[Hwang, J.-Y.]
- Issue Date
- 2021
- Publisher
- USENIX Association
- Citation
- Proceedings of the 15th USENIX Symposium on Operating Systems Design and Implementation, OSDI 2021, pp.147 - 162
- Indexed
- SCOPUS
- Journal Title
- Proceedings of the 15th USENIX Symposium on Operating Systems Design and Implementation, OSDI 2021
- Start Page
- 147
- End Page
- 162
- URI
- https://scholarworks.bwise.kr/skku/handle/2021.sw.skku/99431
- ISSN
- 0000-0000
- Abstract
- The NVMe zoned namespace (ZNS) is emerging as a new storage interface, where the logical address space is divided into fixed-sized zones, and each zone must be written sequentially for flash-memory-friendly access. Owing to the sequential write-only zone scheme of the ZNS, the log-structured file system (LFS) is required to access ZNS solid-state drives (SSDs). Although SSDs can be simplified under the current ZNS interface, its counterpart LFS must bear segment compaction overhead. To resolve the problem, we propose a new LFS-aware ZNS interface, called ZNS+, and its implementation, where the host can offload data copy operations to the SSD to accelerate segment compaction. The ZNS+ also allows each zone to be overwritten with sparse sequential write requests, which enables the LFS to use threaded logging-based block reclamation instead of segment compaction. We also propose two file system techniques for ZNS+-aware LFS. The copyback-aware block allocation considers different copy costs at different copy paths within the SSD. The hybrid segment recycling chooses a proper block reclaiming policy between segment compaction and threaded logging based on their costs. We implemented the ZNS+ SSD at an SSD emulator and a real SSD. The file system performance of the proposed ZNS+ storage system was 1.33–2.91 times better than that of the normal ZNS-based storage system. © 2021 by The USENIX Association. All rights reserved.
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Collections - Computing and Informatics > Computer Science and Engineering > 1. Journal Articles
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