Patent ID: 7953946

Claim:
A method for controlling data retention of a collection of data in a data store, said method comprising: receiving an instruction to store a shadow collection of data to the data store, said shadow collection of data comprising changes to an original volume, said data store having a previous version of the shadow collection of data so that the shadow collection is related to the previous shadow collection; identifying an available amount of data storage space on the data store, said identifying comprising querying the identified available amount of data storage space on a per-block basis and based on the response to the querying, calculating an underestimated, specific amount as a safe available area on the data store; estimating an amount of data storage space needed for storing the shadow collection of data to the data store based on the received instruction; determining whether the identified available amount of data storage space is sufficient for storing the estimated amount of data storage space; and in response to the determining that the identified available amount of data storage space is insufficient for storing the estimated amount of data storage space for the shadow collection, storing only files and not partial blocks of files of the portion of the shadow collection if not all blocks of the files can be fitted in the identified available amount of data storage space, wherein the previous version of the shadow collection of data is deemed valid and forbidden from deletion by a user, and wherein storing comprises rejecting the received instruction when the available amount of data storage space is less than the estimated amount of data storage space so that the valid version of the shadow collection of data is not deleted, overwritten or removed.