Techniques of Evicting Data from NVRAM in the TridentFS Hybrid Storage based File System

• Main Authors: Tzu-YuanHung, 洪梓原
• Other Authors: Da-Wei Chang
• Format: Others
• Language: en_US
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/01328383364723793494

碩士 === 國立成功大學 === 資訊工程學系碩博士班 === 98 === The TridentFS is a hybrid storage file system which combines three popular devices: NVRAM, hard disk drive and SSD. Each device stores different type of data according to the data access patterns. Specifically, the high speed NVRAM stores both frequently-accessed metadata and small files and the hard disk is taken as a high volume storage device for sequentially-accessed large files. The SSD is employed as an extension of NVRAM in case of NVRAM exhaustion. With this data separation, the overall performance can be significantly improved. To handle the size limitation of NVRAM, we setup an eviction mechanism and a more fine-grained and precise eviction policy is proposed to improve the performance by reducing the SSD I/O. We separate inode from data for reducing the extra I/O caused by fake files. On eviction victim selection, we consider more factors: recency, frequency and size against original eviction policy of TridentFS, to more precisely choose the eviction victims and let most I/O occur in NVRAM. In addition, the SSD file layout design is proposed to increase the performance of directory entry searching when using existing file system on SSD. By using the design, TridentFS can release excessive file pressure on a single directory of SSD to complement the shortage of directory entry searching on underlying file system. By using precise eviction policy, TridentFS can demonstrate up to 34.12% improvement in read/write throughput and up to 26.71% reduction of SSD I/O. By using new file layout design on SSD, TridentFS can perform up to 74.53% in time reduction against original TridentFS.