Design And Implementation Of The File System For Shingled Magnetic Recording

In the past three decades, the capacity of single drive has been continually increasing. However, it is approaching the theoretical limit caused by the superparamagnetic effect. The shingled magnetic recording(SMR) is regarded as the most feasible way among new technologies, since it can increase the storage density greatly with little change to the disk structure. But the SMR still cannot take the place of traditional hard drive, as it has a bad performance when doing the random write.An SMR device emulator and a FUSE-based SMR-aware file system is implemented to handle with the bad performance of random write. The device emulator is used to emulate the read and write behavior of real SMR drive, and the file system is used to manipulate the data on the emulated drive. They cooperate as a unity. The file system is divided into the unshingled partition and the shingled partition, which saves the system metadata and file data respectively. In the meantime, a cache module, a file log module and garbage collection module are implemented. The cache module is used to load the data in the SMR device emulator to accelerate the file IO process. The log module saves the addition and removal of files, thus distinguishing between the valid and invalid data on the disk. Research of the garbage collection mechanism of the SMR file system is done to solve the problem of generating invalid data when updating and deleting files, using three garbage collecting strategies.The experiment result shows that the expense of additional operation would drop to 5.9% little by little as the amount of data handled by the file system increase. Therefore, this file system is suitable to work under heavy workload. In the meantime, according to the performance of three garbage collecting strategies, the strategy which is based on cold and hot data partition works the best for the file system in the long term.