Patent ID: 7827193

Claim:
A file sharing system comprising: a migration source file sharing device; a migration destination file sharing device; a first communication channel for connecting a higher level device, the migration source file sharing device, and the migration destination file sharing device; and a second communication channel provided separately from the first communication channel for mutually connecting the migration source file sharing device and the migration destination file sharing device; wherein the migration destination file sharing device generates a migration destination volume in the migration destination file sharing device as a virtual volume of a migration source volume of the migration source file sharing device, wherein the migration destination file sharing device determines a usage percentage of the migration source volume by the higher level device via the first communication channel, wherein if the usage percentage of the migration source volume exceeds a threshold value, the migration destination file sharing device associates a first logical volume, configured by a certain physical device of the migration destination file sharing device, and the migration destination volume, migrates data stored in the migration source volume to the first logical volume by block unit of data via the second communication channel, and writes data to the first logical volume in response to write requests from the higher level device to the migration destination volume after migration, and wherein if the usage percentage of the migration source volume does not exceed the threshold value, the migration destination file sharing device associates a second logical volume configured by pool storage area of physical devices of the migration destination file sharing device and the migration destination volume, migrates data stored in the migration source volume to the second logical volume by file unit of data via the first communication channel, allocates storage area from the pool storage area to the second logical volume by file unit of data during the migration, and allocates storage area from the pool storage area to the second logical volume in response to write requests from the higher level device to the migration destination volume after migration.