System generates data structure based on unique identifiers of objects in storages and sets indicators in positions corresponding to hashes of unique identifiers of objects. The system copies active objects from one storage to another, if number of active objects in storage does not satisfy threshold, and resets indicators in positions in data structure corresponding to hashes of unique identifiers of active objects copied to the other storage. The system generates another data structure based on unique identifiers created while generating data structure, positions in other data structure corresponding to hashes of the unique identifiers. System sets indicators in positions in the other data structure corresponding to hashes of unique identifiers of data objects in active storages while generating data structure. System resets indicators in positions in data structure corresponding to hashes of the unique identifiers corresponding to indicators set in positions of the other data structure.