1. A system, comprising: a processor configured to: receive an indication to perform a backup operation on a plurality of storage areas of a source system; in response to the indication, perform the backup operation including by generating a plurality of snapshots corresponding to respective ones of the plurality of storage areas associated with the backup operation; maintain, at the source system, deduplication data corresponding to one or more data blocks that have already been written to backup media during the backup operation, wherein the deduplication data comprises a plurality of identifiers corresponding to respective ones of data blocks that have already been written to the backup media; and use the deduplication data, at the source system, to deduplicate backup data across the plurality of snapshots associated with the backup operation, wherein to use the deduplication data comprises to compare, at the source system, an identifier associated with a data block to back up in a first snapshot included in the plurality of snapshots to the plurality of identifiers, wherein in response to a determination that a matching identifier is not found in the plurality of identifiers: determine, at the source system, that the data block has not already been written to the backup media; send, from the source system, to a backup storage underlying data of the data block to be stored as an entry associated with the data block in the first snapshot at the backup media at the backup storage; and send, from the source system, to the backup storage a metadata block corresponding to the data block, wherein the metadata block is to be stored in the first snapshot at the backup media at the backup storage, wherein the metadata block is configured to be used to determine to which file or directory, or both, the data block belongs; and a memory coupled to the processor and configured to store the deduplication data.