VMware, Inc.
Read performance of log-structured file system (LFS)-based storage systems that support copy-on-write (COW) snapshotting

Abstract:

Techniques for improving the read performance of an LFS-based storage system that supports COW snapshotting are provided. In one set of embodiments, the storage system can implement an intermediate map for each storage object in the system that is keyed by a composite key consisting of snapshot identifier (major key) and LBA (minor key). With this approach, contiguous logical block addresses (LBAs) of a storage object or its snapshots will map to contiguous <Snapshot ID, LBA>-to-PBA mappings in the storage object's intermediate map, resulting in good spatial locality for those LBAs and robust read performance.