A tree data structure for a file is maintained. The tree data structure is used to capture different versions of the file at different moments of time. An access pattern associated with the file stored on a storage system is determined based at least in part on time-series data associated with the file using the tree data structure that captures different versions of the file at different moments in time. The determined access pattern indicates a period for which the file is likely to be accessed. The file is migrated from a secondary storage tier to a primary storage tier.