Abstract: Techniques for a method of estimating deduplication potential are disclosed herein. The method includes steps of selecting randomly a plurality of data blocks from a data set as a sample of the data set, collecting fingerprints of the plurality of data blocks of the sample, identifying duplicates of fingerprints of the sample from the fingerprints of the plurality of data blocks, estimating a total number of unique fingerprints of the data set depending on a total number of the duplicates of fingerprints of the sample based on a probability of fingerprints from the data set colliding in the sample, and determining a total number of duplicates of fingerprints of the data set depending on the total number of the unique fingerprints of the data set.

Abstract: A method performed in a system that has a plurality of volumes stored to storage hardware, the method including generating, for each of the volumes, a respective space saving potential iteratively over time and scheduling space saving operations among the plurality of volumes by analyzing each of the volumes for space saving potential and assigning priority of resources based at least in part on space saving potential.

Abstract: A method performed in a system that has a plurality of volumes stored to storage hardware, the method including generating, for each of the volumes, a respective space saving potential iteratively over time and scheduling space saving operations among the plurality of volumes by analyzing each of the volumes for space saving potential and assigning priority of resources based at least in part on space saving potential.

Abstract: A method performed in a system that has a plurality of volumes stored to storage hardware, the method including generating, for each of the volumes, a respective space saving potential iteratively over time and scheduling space saving operations among the plurality of volumes by analyzing each of the volumes for space saving potential and assigning priority of resources based at least in part on space saving potential.

Abstract: A method and system for generating data fingerprints is used to de-duplicate a data set having a high level of redundancy. A fingerprint generator generates a data fingerprint based on a data window. Each byte of the data set is added to the fingerprint generator and used to detect an anchor within the received data. If no anchor is detected, the system continues receiving bytes until a predefined window size is reached. When the window size is reached, the system records a data fingerprint based on the data window and resets the window size. If an anchor is detected, the system extends the window size such that the window ends a specified length after the location of the anchor. If the extended window is greater than a maximum size, the system ignores the anchor. The generated fingerprints are compared to a fingerprint database. The data set is then de-duplicated by replacing matching data segments with references to corresponding stored data segments.

Abstract: A method and system for emulating tape library commands is disclosed. Tape library commands implemented in response to commands received from a data protection application are emulated in a disk based storage medium so that existing data protection applications may be used to copy data to and from the disk based storage medium.

Abstract: A system for synchronizing a secondary volume with a primary volume in a continuous data protection system includes scanning means for scanning a region of the primary volume; comparing means for comparing the scanned region with a corresponding region of the secondary volume; storing means for storing an identification of the scanned region in a compare delta map when the comparing means returns a discrepancy between the scanned region and the corresponding region; copying means for copying data from the primary volume to the secondary volume, using the compare delta map as a guide to locate the data to copy; and revising means for revising the compare delta map by removing any changes made to the primary volume during a scan interval, which is a period of time required to scan the primary volume.

Abstract: A method and apparatus for managing backup data is disclosed. A data backup system defines a plurality of time windows for creating and maintaining backup data in accordance with a data backup policy. Each of the time windows is assigned a predetermined amount of storage space. When the data backup system creates backup data, the system determines whether a storage space assigned to a time window is large enough to accommodate new backup data. If the storage space is large enough, the new backup data is stored. However, if the storage space is not large enough, the system deletes the oldest backup data until enough storage space is obtained.

Abstract: A system for the storage and retrieval of data files includes a data disk, a configuration disk and a controller. Each data file includes one or more data blocks, each data block comprising a data section. The data disk stores the data blocks and is divided into a plurality of block groups. The configuration disk stores a copy of at least a portion of the corresponding meta-data. The controller controls both the data disk and the configuration disk.

Abstract: A method for tracking changes on a primary volume in a continuous data protection system writes data to the primary volume. A copy of the data is written to a secondary volume, the secondary volume including all writes made to the primary volume. Each write made to the secondary volume is mapped in a data structure, such that the data structure tracks changes on the primary volume between two different points in time.

Abstract: A method for browsing objects on a protected volume in a continuous data protection system begins by displaying a list of top-level objects to a user who selects a top-level object to browse. A snapshot is selected from the selected top-level object and is decoded. A list of objects in the selected snapshot is displayed and the user selects an object to browse. The selected object is decoded and operations are performed on the selected object. The user can browse the protected volume by snapshots in the top-level object or by a range of time of coverage of the top-level object.

Abstract: The invention is a method and system for copying backup data to a virtual tape library (VTL), where data written to the VTL can optionally be stored on removable disk media for offsite storage. The invention minimizes dependency on tape media without taxing the resources of any of the servers and without the need for the data protection application (DPA) to perform a second backup pass. Backup data written to the VTL can optionally be copied to the VTL's default storage area and/or to a predetermined set of disks that may be removed and stored offsite.

Abstract: A method and system for generating a snapshot in a consistent state is disclosed. The system comprises a host computer, a primary data storage, a data protection unit, and a secondary data storage. The data protection unit monitors a state of an application which is running on the host computer. The data protection unit generates a snapshot of data stored in a primary data storage when the application is in a consistent state, and stores the snapshot on a secondary storage. In the event of a system failure, the data is recovered using the last snapshot.

Abstract: The present invention is a tape library comprising both a small front-end portion and a larger back-end portion. The front-end portion is a visible virtual or physical tape library; and the back-end portion is a large invisible virtual or physical tape vault. The DPA is a typical DPA which only sees the front-end library. If desired, all messages regarding the importing and exporting of tapes are reviewed by an agent. The agent manages the automatic transfer of tapes between the front-end and the back-end, and notifies the user when a manual import or export is needed. This greatly reduces both the amount of hardware required to establish a virtual or physical tape library and also reduces the amount of labor required by a user to physically import and export tapes. If both the front-end library and the back-end vault are virtual and reside on the same virtual tape library appliance, no data movement is necessary and the tapes can be moved merely by performing small software state changes.

Abstract: A method and system for efficiently storing and transferring data in a virtual tape library environment is disclosed. Data is written to a virtual tape library that emulates a physical tape library. Data stored in the virtual tape library may be compressed and an estimated compression ratio may be dynamically computed. While data is written to the virtual tape library, an end-of-tape signal is provided based on the estimated compression ratio.

Abstract: A method for synchronizing a secondary volume with a primary volume in a continuous data protection system begins by scanning a region of the primary volume, which is then compared with a corresponding region of the secondary volume. An identification of the scanned region is stored in a compare delta map when the comparison results in a discrepancy between the scanned region and the corresponding region. Data is copied from the primary volume to the secondary volume, using the compare delta map as a guide to locate the data to copy. If the data protection system has failed just prior to the restore process being initiated, it is termed a re-baseline, and the entire primary volume is scanned. If the data protection system is active prior to the restore process being initiated, it is termed a re-synchronization, and is optimized by scanning only select regions of the primary volume.

Abstract: A method and system where data is maintained in a continuous data protection system is disclosed. A primary volume may be protected according to an any-point-in-time (APIT) window wherein restores may be performed at any time as desired. The APIT window may be of any time duration as desired. Outside of the APIT window, a retention policy for phasing out data may be established as desired.

Abstract: A method for stream allocation in a data storage system begins by determining whether a stream needs storage space. Storage space for the stream is requested, and a device on which to allocate the storage space is selected. The storage space on the selected device is allocated to the stream.

Abstract: A system for synchronizing a secondary volume with a primary volume in a continuous data protection system includes scanning means for scanning a region of the primary volume; comparing means for comparing the scanned region with a corresponding region of the secondary volume; storing means for storing an identification of the scanned region in a compare delta map when the comparing means returns a discrepancy between the scanned region and the corresponding region; copying means for copying data from the primary volume to the secondary volume, using the compare delta map as a guide to locate the data to copy; and revising means for revising the compare delta map by removing any changes made to the primary volume during a scan interval, which is a period of time required to scan the primary volume.

Abstract: In a continuous data protection system having a primary volume and a secondary volume, a method for data recovery begins by selecting a snapshot of the primary volume to be recovered and a location on which the snapshot is to be loaded. A point in time (PIT) map is created for the selected snapshot, and the selected snapshot is loaded at the selected location. A data block from the PIT map is resolved to determine which block on the secondary volume is presented as being part of the snapshot. The snapshot is accessed via a host computer as if the snapshot was the primary volume at an earlier point in time, corresponding to the time of the selected snapshot.