Abstract: Described are various embodiments of methods, systems, devices and appliances relating to virtualized application-layer space for data processing in such data storage systems, including a distributed data storage system, and methods relating thereto, for implementing application-specific data processing of stored client data, the data storage system comprising: a plurality of communicatively coupled data storage components, each data storage component comprising at least one data storage resource and a processor, the plurality of data storage components maintaining a data object store of client data, said client data being stored in said data object store in accordance with a data object store file system; and a virtualized processing unit instantiated implementing application-specific data processing of said client data stored on the data object store, said client data object store accessible by said virtualized processing unit in accordance with an application-specific data storage access protocol.