A fully persistent and consistent read/write cache using flash-based general SSDs for desktop workloads. (June 2016)

• Record Type: Journal Article
• Authors: Baek, Sung Hoon; Park, Ki-Woong
• Is Part Of: Information systems. Volume 58(2016)
• Page Start: 24
• Page End: 42
• Publication Date: 2016-06
• Subjects: Secondary storage; Database management -- Periodicals; Electronic data processing -- Periodicals; Bases de données -- Gestion -- Périodiques; Informatique -- Périodiques; Database management; Electronic data processing; Periodicals; 005.7
• DOI: 10.1016/j.is.2016.02.002
• Languages: English
• ISSNs: 0306-4379

Abstract

Abstract: The flash-based SSD is used as a tiered cache between RAM and HDD. Conventional schemes do not utilize the nonvolatile feature of SSD and cannot cache write requests. Writes are a significant, or often dominant, fraction of storage workloads. To cache write requests, the SSD cache should persistently and consistently manage its data and metadata, and guarantee no data loss even after a crash. Persistent cache management may require frequent metadata changes and causes high overhead. Some researchers insist that a nonvolatile persistent cache requires new additional primitives that are not supported by general SSDs in the market. We proposed a fully persistent read/write cache, which improves both read and write performance, does not require any special primitive, has a low overhead, guarantees the integrity of the cache metadata and the consistency of the cached data, even during a crash or power failure, and is able to recover the flash cache quickly without any data loss. We implemented the persistent read/write cache as a block device driver in Linux. Our scheme aims at virtual desktop infra servers. So the evaluation was performed with massive, real desktop traces of five users for ten days. The evaluation shows that our scheme outperforms an LRU version of SSD cache by 50% and the read-only version of our scheme by 37%, on average, for all experiments. This paper describes most of the parts of our scheme in detail. Detailed pseudo-codes are included in the Appendix. Abstract : Highlights: We proposed a fully persistent read/write cache. It guarantees persistency and consistency of dirty data even at a crash or a power failure using general SSDs. It quickly recovers the flash cache without any data loss. We implemented this scheme in Linux. The evaluation was performed with real workloads, and showed our scheme outperforms another flash cache by 50%.