1. A computer-implemented method comprising: receiving requests to store a plurality of data objects in a storage system, the storage system having a primary storage and a secondary storage; adding a data object to one of a plurality of files in the secondary storage, the file storing the plurality of data objects; generating index data including an offset location for each data object and a size of each data object in the file in the secondary storage; and storing the index data in the primary storage for locating data objects in the file in the secondary storage.