A New LSM-style Garbage Collection Scheme for ZNS SSDs


Gunhee Choi, Kwanghee Lee, Myunghoon Oh, and Jongmoo Choi, Dankook University; Jhuyeong Jhin and Yongseok Oh, SK Hynix


This paper explores how to design a garbage collection scheme for ZNS (Zoned NameSpace) SSDs (Solid State Drives). We first show that a naive garbage collection based on a zone unit incurs a long latency due to the huge size of a zone. To overcome this problem, we devise a new scheme, we refer to it as LSM_ZGC (Log-Structured Merge style Zone Garbage Collection), that makes use of the following three features: segment based fine-grained garbage collection, reading both valid and invalid data in a group manner, and merging different data into separate zones. Our proposal can exploit the internal parallelism of a zone and reduce the utilization of a candidate zone by segregating hot and cold data. Real implementation based experimental results show that our scheme can enhance performance by 1.9 times on average.

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@inproceedings {254268,
author = {Gunhee Choi and Kwanghee Lee and Myunghoon Oh and Jongmoo Choi and Jhuyeong Jhin and Yongseok Oh},
title = {A New {LSM-style} Garbage Collection Scheme for {ZNS} {SSDs}},
booktitle = {12th USENIX Workshop on Hot Topics in Storage and File Systems (HotStorage 20)},
year = {2020},
url = {https://www.usenix.org/conference/hotstorage20/presentation/choi},
publisher = {USENIX Association},
month = jul

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