Epoch-based management of file system data is disclosed. In various embodiments, for each of a plurality of snapshots, data that associates with the snapshot a corresponding last chunk identifier assigned as of a time at which the snapshot is or was created is stored a in a first data structure. For each of a plurality of chunks of file system data no longer referenced by any live file system object, an epoch identifier associated with an epoch in which the chunk became no longer referenced by any live file system object is stored in a second data structure. A chunk identifier and associated epoch comprising an entry in the second data structure are compared with one or more entries in the first data structure to determine whether a chunk associated with the chunk identifier is associated with a snapshot that continues to be retained.
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