NETWORK-ACCESSIBLE BLOCK-LEVEL SNAPSHOTS

The present application relates to a public snapshot service for creating and managing block-level snapshots. The public snapshot service can create a snapshot using (i) a specification of a parent snapshot to be used as a basis for a snapshot, and (ii) a specification of the data blocks to be backed up in the snapshot. The data blocks in the snapshot may be stored in a specific storage path structure that facilitates computation of a block difference with respect to the parent snapshot. Storage locations for each block that comprise the snapshot can be enumerated on a snapshot manifest. Identification of storage location for a requested snapshot block can be improved using a manifest index. Snapshots can be configured to enable writing at the sub-block level. Subsequent modifications made to block storage volume that forms the basis of the snapshots can be backed up as a sub-block level operation.