Virtual Allocation: A Scheme for Flexible Storage Allocation

Traditional file systems allocate and tie up entire storage space at the time the file system is created. This creates a situation where one file system could be running out of space, while another file system has ample unused storage space. In such environment, storage management flexibility is seriously hampered. This paper presents virtual allocation, a scheme for flexible storage allocation. It separates storage allocation from file system. It employs dynamic allocation strategy based on time of write, which lets applications fit into the actual usage of storage space without regard to configured file system size. Unused storage space can be provided to any application or file system as the needs arise. This improves flexibility by allowing us to share storage space across different file systems. It also makes it possible for a storage device to be expanded easily to other available storage resources because storage allocation is not tied to file systems. This paper presents the design of virtual allocation and an evaluation of it through benchmarks. To illustrate our approach, we implemented a prototype system on PCs running Linux. We present the results from the prototype implementation and its evaluation.