Extending Lifetime and Reducing Garbage Collection Overhead of Solid State Disks with Virtual Machine Aware Journaling

Abstract

Virtualization is becoming widely deployed in commercial servers. In our previous study, we proposed Virtual Machine Aware journaling (VMA journaling), a file system journaling approach for virtual server environments. With reliable VMM and hardware subsystems, VMA journaling eliminates journal writes while ensuring file system consistency and data integrity in virtual server environments, allowing it to be an effective alternative to traditional journaling approaches in these environments. In recent years, solid-state disks (SSDs) have shown their potential as a replacement of traditional magnetic disks in commercial servers. In this paper, we demonstrate the benefits of VMA journaling on SSDs. We compare the performance of VMA journaling and three traditional journaling approaches (i.e., the three journaling modes of the ext3 journaling file system) in terms of lifetime and garbage collection overhead, which are two key performance metrics for SSDs. Since a Flash Translation Layer (FTL) is used in an SSD to emulate traditional disk interface and the SSD performance highly depends on the FTL being used, three state-of-the-art FTLs (i.e., FAST, Super Block FTL and DFTL) are implemented for performance evaluation. The performance results show that, traditional full data journaling could reduce the lifetime of the SSD significantly. VMA journaling extends the SSD lifetime under full data journaling by up to 86.5%. Moreover, GC overhead is reduced by up to 80.6% when compared to the full data journaling approach of ext3. Finally, VMA journaling is effective under all the FTLs. These results demonstrate that VMA journaling is effective in SSD-based virtual server environments.