Flexible, modular file volume virtualization in Loris

Traditional file systems made it possible for administrators to create file volumes, on a one-file-volume-per-disk basis. With the advent of RAID algorithms and their integration at the block level, this “one file volume per disk” bond forced administrators to create a single, shared file volume across all users to maximize storage efficiency, thereby complicating administration. To simplify administration, and to introduce new functionalities, file volume virtualization support was added at the block level. This new virtualization engine is commonly referred to as the volume manager, and the resulting arrangement, with volume managers operating below file systems, has been referred to as the traditional storage stack. In this paper, we present several problems associated with the compatibility-driven integration of file volume virtualization at the block level. In earlier work, we presented Loris, a reliable, modular storage stack, that solved several problems with the traditional storage stack by design. In this paper, we extend Loris to support file volume virtualization. In doing so, we first present “File pools”, our novel storage model to simplify storage administration, and support efficient file volume virtualization. Following this, we will describe how our single unified virtualization infrastructure, with a modular division of labor, is used to support several new functionalities like (1) instantaneous snapshoting of both files and file volumes, (2) efficient snapshot deletion through information sharing, and (3) open-close versioning of files. We then present “Version directories,” our unified interface for browsing file history information. Finally, we will evaluate the infrastructure, and provide an in-depth comparison of our approach with other competing approaches.