Abstract
Because virtual machine monitor (VMM) provides a secure, reliable and fully isolated virtual execution environment, it offers a novel solution to improve security, reliability and increase system utilization. However, because every virtual machine operates independently and utilizes individual disk partitions, disk seek time can easily increase when accessing different disk partitions. Further, VMM checks every I/O access of the virtual machine to ensure that no one can corrupt the system. Thus, it results in higher I/O access overhead under virtual machine architecture then under traditional operating system. So, it is important to adapt the filesystem to the virtual execution environment to improve performance. Journaling filesystems adopt metadata journaling technique to improve filesystem performance and consistency. However, the cost brings by metadata journaling is extra disk space and performance degradation caused by frequent journal data flushing. In addition, the problem is intensified due to the limitations of virtual machine architecture as discussed above. In this thesis, we propose a framework that modifies both the journaling filesystem and the VMM to alleviate the overhead. We only log necessary information of file buffer caches in the VMM and protect them from being tainted via the use of VMM. By using this mechanism we eliminate the need for extra disk space while still retaining same filesystem consistency. Experimental data suggests our method improves journaling filesystem performance by 30% to 150% and speeds up the filesystem recovery process by 2 to 6 times faster.