A storage service system includes a storage service user (SSU) which uses a data
accumulation service, and a storage service provider (SSP) which provides a user
terminal with a data accumulation area. The SSU monitors a free capacity of its
own data accumulation unit such that the free capacity cannot be smaller than a
predetermined value, and automatically transfers stored data to the SSP through
a network when the free capacity becomes close to the predetermined value. Thus,
the SSU can reserve a constant free capacity.
