A mechanism is provided for backing up metadata in a data storage system. Given metadata stored on the data storage system is implemented by way of a tree structure operable by fixed mapping. A stream of snapshots is taken of leaves in the metadata tree structure of given metadata stored on persistent data storage. The metadata tree structure of the given metadata stored on the persistent data storage is reconstructed on a basis of the stream of snapshots taken for backing up the given metadata stored on the persistent data storage. A journal over the reconstructed metadata tree structure is then replayed. In response to a given status discrepancy being flagged in respect of any given metadata, the status of a given leaf corresponding thereto in the reconstructed data tree structure is modified for consistency with the corresponding journal entry in the journal for that given metadata.