A space-efficient change journal for a storage system is provided. The storage system includes a memory having computer readable instructions stored therein. The system further includes a processor configured to access a log structure merge (LSM) tree-based metadata index having metadata for the storage system. The LSM tree-based metadata index includes indices placed in a plurality of indexing layers and one or more indices are merged within the indexing layers in response to updates to metadata, or as a background task. The processor is configured to identify one or more indices of the LSM tree-based metadata index as entries of a change journal of the storage system. The processor is further configured to maintain the change journal of the storage system based upon the identified entries.