1. A method for copying forward live clumps stored in storage regions used by a file system, the method comprising: during a storage-region-identifying phase, executing a plurality of container-identifying workers to identify a set of storage regions that contain clumps that correspond to a set of live-clump-references; wherein live-clump-references are references to clumps that belong to live objects in the file system; wherein the plurality of container-identifying workers execute independent of each other; wherein each container-identifying worker identifies one or more storage regions that contain clumps that correspond to the set of live-clump-references; during a copy-forward phase that occurs after the storage-region-identifying phase, executing a plurality of copy-forward task workers to perform copy-forward operations on the set of storage regions; wherein the plurality of copy-forward task workers execute independent of each other; and wherein each copy-forward task worker is assigned a subset of storage regions from the set of storage regions, and performs copy-forward operations on the subset of storage regions to which the copy-forward task worker was assigned.