Ajou University repository

We Ain’t Afraid of No File Fragmentation: Causes and Prevention of Its Performance Impact on Modern Flash SSDs
  • Jun, Yuhun ;
  • Park, Shinhyun ;
  • Kang, Jeong Uk ;
  • Kim, Sang Hoon ;
  • Seo, Euiseong
Citations

SCOPUS

0

Citation Export

Publication Year
2024-01-01
Journal
Proceedings of the 22nd USENIX Conference on File and Storage Technologies, FAST 2024
Publisher
USENIX Association
Citation
Proceedings of the 22nd USENIX Conference on File and Storage Technologies, FAST 2024, pp.193-208
Mesh Keyword
Allocation algorithmDegraded performanceMemory accessPerformancePerformance degradationPerformance impactRead performanceSolid state disksSplittingsThree-level
All Science Classification Codes (ASJC)
Computer Networks and CommunicationsHardware and ArchitectureSoftware
Abstract
A few studies reported that fragmentation still adversely affects the performance of flash solid-state disks (SSDs) particularly through request splitting. This research investigates the fragmentation-induced performance degradation across three levels: kernel I/O path, host-storage interface, and flash memory accesses in SSDs. Our analysis reveals that, contrary to assertions in existing literature, the primary cause of the degraded performance is not due to request splitting but stems from a significant increase in die-level collisions. In SSDs, when other writes come between writes of neighboring file blocks, the file blocks are not placed on consecutive dies, resulting in random die allocation. This randomness escalates the chances of die-level collisions, causing deteriorated read performance later. We also reveal that this may happen when a file is overwritten. To counteract this, we propose an NVMe command extension combined with a page-to-die allocation algorithm designed to ensure that contiguous blocks always land on successive dies, even in the face of file fragmentation or overwrites. Evaluations with commercial SSDs and an SSD emulator indicate that our approach effectively curtails the read performance drop arising from both fragmentation and overwrites, all without the need for defragmentation. Representatively, when a 162 MB SQLite database was fragmented into 10,011 pieces, our approach limited the performance drop to 3.5%, while the conventional system experienced a 40% decline.
Language
eng
URI
https://aurora.ajou.ac.kr/handle/2018.oak/37159
https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85194147696&origin=inward
DOI
https://doi.org/2-s2.0-85194147696
Type
Conference
Funding
We thank the anonymous reviewers and our shepherd, Peter Desnoyers, for their valuable suggestions for this paper. This research was supported by Samsung Electronics, and by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (2021R1A2C200497612).
Show full item record

Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.

Related Researcher

Kim, Sang-Hoon Image
Kim, Sang-Hoon김상훈
Department of Software and Computer Engineering
Read More

Total Views & Downloads

File Download

  • There are no files associated with this item.