The cost of a conventional centralized file server is high; though such a system is suited for a learning environment such as in schools. However, our university has several hundreds PCs whose HDDs are not usually used. The total size of these unused capacities of the HDDs is nearly equal to the capacity of a file server. Thus, in this paper, we propose a java-based toolkit to construct a virtual large-scale storage system. We call it VLSD (Virtual Large-scale Disk). This toolkit is implemented by Java and consists of RAID (Redundant Arrays of Inexpensive/Independent Disks) and NBD (Network Block Device). Using VLSD, we show how to construct a large disk that consists of multiple idle spaces distributed in networks. VLSD supports typical RAID classes and other utility classes. These can be combined freely with each other.