Abstract: Examples implementations relate to journals for metadata changes. An example includes detecting, by a storage controller, metadata changes associated with a container index of a deduplication storage system; recording, by the storage controller, the detected metadata changes in a journal associated with the container index, where the journal is included in a journal group comprising a plurality of journals; determining, by the storage controller, whether a filled amount of the journal exceeds a fill threshold; and, in response to a determination that the filled amount of the journal does not exceed the fill threshold, writing the journal group from memory to persistent storage.

Abstract: Examples implementations relate to journals for metadata changes. An example includes detecting, by a storage controller, metadata changes associated with a container index of a deduplication storage system; recording, by the storage controller, the detected metadata changes in a journal associated with the container index, where the journal is included in a journal group comprising a plurality of journals; determining, by the storage controller, whether a filled amount of the journal exceeds a fill threshold; and, in response to a determination that the filled amount of the journal does not exceed the fill threshold, writing the journal group from memory to persistent storage.

Abstract: Examples are disclosed including generation of a first erasure coded data portion based on a first data portion of the data object, generation of a second erasure coded data portion based on a second data portion of the data object, formation of a first combined block by combining a first part of the first erasure coded data portion and a first part of the second erasure coded data portion, formation of a second combined block by combining a second part of the first erasure coded data portion and a second part of the second erasure coded data portion, storage of the first combined block in a first storage location, and storage of the second combined block in a second storage location.

Abstract: Examples are disclosed including generation of a first erasure coded data portion based on a first data portion of the data object, generation of a second erasure coded data portion based on a second data portion of the data object, formation of a first combined block by combining a first part of the first erasure coded data portion and a first part of the second erasure coded data portion, formation of a second combined block by combining a second part of the first erasure coded data portion and a second part of the second erasure coded data portion, storage of the first combined block in a first storage location, and storage of the second combined block in a second storage location.

Abstract: Examples disclosed herein relate to restoration of a storage volume. In an example, a backup of a snapshot of a storage volume may be stored on a backup device. An allocation map for the snapshot may be stored in a data store on the backup device. The respective backups of additional snapshots of the storage volume may be stored on the backup device. For each additional snapshot, a difference map may be stored in the data store. In response to a request to restore the backup of the snapshot, a latest snapshot of the storage volume may be generated. A combined map may be generated based on the difference map for the latest snapshot and respective difference maps of the additional snapshots backed up on the backup device prior to the latest snapshot. The blocks that changed between the snapshot and the latest snapshot may be copied to storage device.

Abstract: In one example, write request for input data record that includes input data and metadata associated with input data. If any input metadata are common metadata, and if length of a common metadata group hash formed from combined common metadata is less than sum of lengths of the input metadata that are common metadata, generate a common metadata hash record to include the common metadata group hash and the common metadata. If any input metadata are common metadata, and if length of a common data group hash formed from the common data is less than sum of lengths of the common data, generate a common data hash record to include the common data group hash and the common data. Generate an output data record to include the common metadata and data group hash of the hash records and include input metadata and data not in the generated hash records.

Abstract: Disclosed is a storage apparatus comprising a data store; a data input; and a data processor arranged to: receive from the data input a block of data to be stored at an append point after sequential data comprising one or more stored blocks of data; retrieve an integrity measure, of one or more stored integrity measures that are associated with one or more respective points in the sequential data, said retrieved integrity measure being associated with a point at or preceding the append point; calculate a new integrity measure using the received block of data and the retrieved integrity measure; and store the received block of data and the new integrity measure in the data store, in addition to at least one stored integrity measure that is associated with a point in the data at or preceding the append point.

Abstract: An apparatus for writing data to a data storage medium on which data is stored in data groups (N?3 to N+1) comprising tracks extending across and spaced from a reference edge of the storage medium includes a control system operable to cause i) a track reference difference value representative of a difference in a distance between the tracks of an existing data group (N?1) on the storage medium and the reference edge and a distance between the reference edge and the tracks of a data group (N) to be written to the storage medium such that it is the next data group following the existing data group (N?1) or ii) data from which such a difference value can be derived to be included in at least one of frame (A1 to A5) to be written between the existing data group and the next data group such that the tracks of the at least one frame are spaced from the reference edge by substantially the same distance as the tracks of the existing data group.

Abstract: A method of storing data received in a data stream from a data source is disclosed in which prior to performing deduplication on the data stream a processor decompresses selected compressed data entities in the data stream to provide a decompressed form of the data entities in the data stream in place of the compressed form, the data stream including the decompressed data entities is deduplicated and the deduplicated data is stored to a deduplicated data store.

Abstract: A method of controlling relative motion of a data storage medium on which data is stored in data groups comprising tracks extending across the storage medium and a rotatable transducer for reading data from the storage medium includes determining from the data groups a start reread data group at which a data reread process is to start following detection of a read error condition in a preceding data read process. The method also includes obtaining a reread track reference value for use in controlling that relative motion during the data reread process using a track reference value difference stored in at least one track of at least one data group that is to be reread during the data reread process and a track reference value that was used in controlling that relative rotation during the preceding data read process.

Abstract: Disclosed is a storage apparatus comprising a data store; a data input; and a data processor arranged to: receive from the data input a block of data to be stored at an append point after sequential data comprising one or more stored blocks of data; retrieve an integrity measure, of one or more stored integrity measures that are associated with one or more respective points in the sequential data, said retrieved integrity measure being associated with a point at or preceding the append point; calculate a new integrity measure using the received block of data and the retrieved integrity measure; and store the received block of data and the new integrity measure in the data store, in addition to at least one stored integrity measure that is associated with a point in the data at or preceding the append point.

Abstract: An apparatus for writing data to a data storage medium on which data is stored in data groups (N?3 to N+1) comprising tracks extending across and spaced from a reference edge of the storage medium includes a control system operable to cause i) a track reference difference value representative of a difference in a distance between the tracks of an existing data group (N?1) on the storage medium and the reference edge and a distance between the reference edge and the tracks of a data group (N) to be written to the storage medium such that it is the next data group following the existing data group (N?1) or ii) data from which such a difference value can be derived to be included in at least one of frame (A1 to A5) to be written between the existing data group and the next data group such that the tracks of the at least one frame are spaced from the reference edge by substantially the same distance as the tracks of the existing data group.

Abstract: A tape data transfer apparatus operable to determine a tape damage condition of a tape received in the apparatus by determining a value representative of a tape pack size of the received tape and comparing the value representative of tape pack size with a tape pack size reference value that is read from the cartridge.

Abstract: A method of controlling relative motion of a data storage medium on which data is stored in data groups comprising tracks extending across the storage medium and a rotatable transducer for reading data from the storage medium includes determining from the data groups a start reread data group at which a data reread process is to start following detection of a read error condition in a preceding data read process. The method also includes obtaining a reread track reference value for use in controlling that relative motion during the data reread process using a track reference value difference stored in at least one track of at least one data group that is to be reread during the data reread process and a track reference value that was used in controlling that relative rotation during the preceding data read process.

Abstract: A tape guide system for supporting magnetic tape about a rotary scan drum of a data transfer apparatus is disclosed. The tape guide system comprises a tape guide and a guide ramp. The tape guide has a supporting surface for supporting the magnetic tape in the tape guide's deployed position and has a non-deployed position in which the supporting surface is spaced from and non-aligned with a surface of the tape to be supported. The tape guide is arranged to be driven relative to the guide ramp towards the deployed position with a horizontal movement component, thereby causing the guide ramp to impart a vertical movement to the tape guide and, in the deployed position, substantially align at least part of the supporting surface of the tape guide with the surface of the tape to be supported. Other systems and methods are also provided.

Abstract: A tape guide system for supporting magnetic tape about a rotary scan drum of a data transfer apparatus is disclosed. The tape guide system comprises a tape guide connected to an arm. The tape guide has a deployed position in which a supporting surface of the tape guide supports the magnetic tape and a non-deployed position in which the supporting surface is spaced from and non-aligned with a surface of the tape to be supported. The arm is arranged to be driven about an axis of rotation towards the deployed position. The axis of rotation of the arm is inclined such that, in the deployed position at least part of the supporting surface of the tape guide is substantially aligned with the surface of the tape to be supported. Other systems and methods are also provided.

Abstract: A tape drive apparatus has at least one rotary head for reading/writing a track. The track has a number of fragments and each fragment has an identifier. The tape drive apparatus has a position indicator apparatus for providing a signal that indicates a rotational position of the head. The combination of the signal and the identifier unequivocally identifies a fragment within the fragments of a track. This has the advantage that non-unique identifiers can be used for the fragments of a track.