A mechanism is provided for multi-tenancy data security. A storage device receives a request for storage from a client device. Responsive to the request for storage being from an existing tenant, the storage device determines whether there is allocated unused storage in a freed space storage pool associated with the existing tenant. Responsive to the allocated unused storage existing in the freed space storage pool, the storage device re-allocates all or a portion of the allocated unused storage existing in the freed space storage pool to an active storage pool associated with the existing tenant in order to satisfy the request such that the client device accesses the allocated unused storage in the active storage pool.