The Cell A cell is the smallest addressable unit within the dCache. In the sense of the dCache it provides a particular subservice, like interfacing the PnfsNamespace, collecting information about free diskspace, controlling the different doors, a.s.o. Classes within a Cell may share all sorts of information, while cells are not allowed to communicate other then by exchanging messages. Consequently, Cells are implemented location independently.
The Domain A domain is a collection of Cells running in a single java virtual machine. Domains are connected by so called tunnels which lets cells of different domains talk to each other. In general the functionallity of a cell doesn't depend on the domain it's running in, as long as the related domains are connected by tunnels. The overall topology setup is managed by the LocationManager. Each Domain has to register to the LocationManager and gets further tunnel building commands from there.
The Pool A pool is a disk partition or part of it with a defined size. A pool can not span disk partitions. In addition, a pool in our sense is the cell which is responsible for exactly this part of the disk. A pool has a name which is ( or has to be ) unique in the context of a single dCache instance.
The PoolDomain A PoolDomain is a Domain running at least one PoolCell. The current setup allows only one PoolDomain per host running an arbitrary number of PoolCells and so serving all disk partitions which belong to pools on that host.
The storageClass The storageClass is the abstraction of an HSM specific organizational unit. Whithin the dCache it's treated as a string value. The syntax depends of the type of HSM.