Mount Time Analysis on a Flash File System with a Checkpoint Mechanism

The mount time is crucial for improving the availability of flash file systems as their capacity levels rapidly increase. A long mount delay time can make the flash file system inappropriate for mobile computers and embedded systems, which require high availability. To reduce the mount delay, flash file systems can use a checkpoint mechanism which takes a snapshot of the runtime file system's state. However, the checkpoint becomes unavailable when the flash file system is not cleanly unmounted (e.g., in the event of a power failure or an abnormal shutdown). This can result in a scan of all of the flash memory to determine the state of the flash file system. Therefore, a periodic checkpoint update method is required to provide a higher level of availability for flash file systems. In this paper, we propose an analytical framework that takes into account the correlation between the failure rate and the write operation rate when estimating the expected mount time. We derive the availability of the checkpoint and the expected mount time in a flash file system with a periodic checkpoint mechanism. Through an analytical evaluation of the mount time, our framework can accurately predict the mount time.