Automated on-line capacity expansion method for storage device

A system comprising:

• a storage system which provides a logical volume;
• and
• a host which sends data to the logical volume of the storage system,
• wherein the storage system includes,
• a plurality of disk devices,
• a controller, coupled to the plurality of disk devices, which manages a plurality of storage areas provided by the plurality of disk devices,
• wherein the host includes,
• an application which sends data to the logical volume, and
• an operating system which manages a block position of the logical volume,
• wherein, if the operating system receives a request from the application to expand a first capacity of the logical volume, the operating system sends a write request to the logical volume,
• wherein, in response to the write request, the controller allocates at least one of the plurality of storage areas to the logical volume, and
• wherein the controller monitors a second capacity of storage areas allocated to the logical volume relative to a third capacity of the plurality of storage areas.