System and method for storing redundant information

A method performed by a computer system of storing a single-instance copy on a sequential storage medium, comprising:

• receiving one or more data objects in a hierarchy,
• wherein some of the data objects are identical;
• storing, on a random-access storage medium, a single-instance copy of the one or more data objects,
• wherein the single-instance copy contains information describing—
• a first instance of each of the one or more data objects, and
• one or more references to the one or more first instances as stored on the random-access storage medium;
• and
• after storing the single-instance copy of the one or more data objects on the random-access storage medium, then storing, on a sequential storage medium, the information describing the hierarchy, the one or more first instances, and the one or more references to the first instances as stored on the sequential storage medium, in that order.

A computer system for restoring data from sequential storage medium, wherein the data has been deduplicated, the system comprising:

• at least one processor;
• at least one data storage device coupled to the at least one processor;
• a receiving unit configured to receive a request to restore at least first and second different data objects from a deduplicated copy of the first and second data objects,
• wherein the deduplicated copy of the first and second data objects is stored on a sequential storage medium,
• wherein the first and second data objects, prior to deduplication and storage on the sequential storage medium, included multiple, identical copies of the first and second data objects, respectively, and
• wherein the deduplicated copy contains one instance, stored on the sequential storage medium, the first and second data objects, and information describing one or more references to the one instance of the first and second data objects;
• an identifying unit, in response to the received request, configured to—
• when a requested first or second data object is stored as an instance, identify a location on the sequential storage medium of the instance of the respective first or second data objects, and
• when a requested first or second data object is stored as a reference to an instance, identify a location on the sequential storage medium of the instance of the respective first or second data objects, and
• configured to sort the identified locations;
• and
• a restoring unit configured to restore the requested data objects to a random-access storage medium from the sorted locations on the sequential storage medium.

A computer system for restoring data from a single-instance copy on a sequential storage medium, comprising:

• a receiving unit configured to receive a request to restore one or more data objects from a single-instance copy of the data objects on a sequential storage medium,
• wherein some of data objects are ore were identical, and
• wherein the single-instance copy contains information describing a first instance of each of the one or more data objects, and one or more references to the first instances as stored on the sequential storage medium;
• an identifying unit configured to, for each of the one or more data objects—
• identify the storage location of the instance when the data object is stored as an instance in the single-instance copy, and
• identify the storage location of the first instance when the data object is stored as a reference to a first instance in the single-instance copy;
• and
• a restoring unit configured to restore the one or more data objects on a random-access storage medium in an order of the identified storage locations on the sequential storage medium.

A non-transitory computer-readable medium containing instructions for controlling a computer system to execute a method of copying a deduplicated copy of data from a sequential storage medium to a random-access storage medium, the method comprising:

• receiving a request to recreate on a random-access storage medium a deduplicated copy of data objects from a sequential medium,
• wherein the deduplicated copy contains information describing a first instance of each of the data objects, and one or more references to the first instances as stored on the sequential storage medium;
• recreating at least a portion of the deduplicated copy on the random-access storage medium,
• wherein the references in the recreated copy refer to first instances as stored on the random-access storage medium;
• receiving a request to restore one of the data objects from the deduplicated copy on the random-access medium to a destination location;
• determining whether the data object is stored as an instance or a reference in the deduplicated copy on the random-access storage medium;
• and
• when the data object is stored as an instance, storing the instance in the destination location, but when the data object is stored as a reference to a first instance, storing, if necessary, the first instance in the destination location.