Patent ID: 7024529

Claim:
A user data backup method by a computer which resides between a user side computer environment and a storage service side computer environment to support storage service, the data backup method comprising: selecting plural storage devices, which satisfy conditions indicated by the user side computer environment, from a plurality of entirely or partially empty storage devices owned by the storage service side computer environment; receiving user data from the user side computer environment; dividing the user data into records of a predetermined size; transmitting the records to the storage service side computer environment so that the records are to be distributed and stored to the selected plural storage devices; and holding storage service side conditions for providing said storage devices owned by said storage service side computer environment; wherein: said storage service side conditions include end data until which the respective storage devices are available, said end dates being registered to memory means, said computer checks if said end dates have passed; if any of said end dates is found to have passed, at least one storage device which satisfies the conditions indicated by the user side computer environment is selected as an alternative, said computer receives at least part of said user data stored in the storage device whose end date has passed, and said computer transmits the received user data to the selected at least one alternative storage device.