摘要:近来出现诸多以非易失性存储器（non-volatile memory，简称NVM）作为存储设备的新型持久化内存文件系统，充分发掘NVM的低延迟和可按字节寻址等优点，优化文件访问的I/O栈和一致性机制，极大提升文件系统的性能.然而，现有持久化内存文件系统都没有考虑NVM写耐受度低的缺陷，极易导致NVM被磨损穿（wear out）.针对NVM写耐受度低的缺点，探索多种利用基本文件操作对NVM造成磨损攻击的方式，并在真实持久化内存文件系统PMFS中以实验证明磨损攻击的严重性.为有效防御针对NVM的磨损攻击，提出了持久化内存文件系统磨损防御机制（persistent in-memory file system wear defense technique，简称PFWD），包括索引节点元数据虚拟化技术、超级块迁移技术、文件数据页磨损均衡技术和文件索引结构迁移技术，保护文件系统中所有可能被磨损攻击利用的数据结构.实验结果证明所提出的PFWD技术能有效地防御病毒发动对NVM的磨损攻击，提高了存储系统的稳定性.



Abstract:Recently, many new persistent in-memory file systems are proposed to exploit the advantages of non-volatile memory (NVM), such as low latency and byte-addressability. As a result, the performance of the persistent in-memory file systems is greatly improved by optimizing the I/O stack and data consistency mechanisms. Nevertheless, existing persistent in-memory file systems ignores the limited write endurance of NVM, which can easily lead to the wear out of NVM. This study first explores wear attacks using the common file system operations to wear out the underlying NVM devices of persistent in-memory file systems. The effectiveness of the wear attacks is proved by experiments in PMFS, a real persistent in-memory file system. Then, in order to prevent NVM from malicious wear attacks, this study proposes a persistent in-memory file system wear defense (PFWD) strategy, which includes inode virtualization, super block migration, data page wear-leveling, and file index structure migration, to protect all the data structures of file systems that may be exploited by wear attacks. Experimental results show that PFWD can effectively prevent NVM from wear attacks and improve the stability of the storage system.



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