International Business Machines Corporation

Masayuki Iwanaga

Yutaka Oishi

Tohru Hasegawa

Yumiko Ohta

Roy Daron Cideciyan

Simeon Furrer

Keisuke Tanaka

Kevin Dale Butt

Mark Alfred Lantz

Atsushi Abe

Ernest Stewart Gale

The present disclosure includes systems and methods for reducing rewrite overhead in a sequential access storage system. The method may comprise writing a data set to a sequential access medium using a magnetic head, wherein the data set comprises a plurality of encoded data blocks, classifying each of the plurality of encoded data blocks on the sequential access medium into one of at least three classes of write quality, and rewriting the encoded data blocks in a rewrite area of the sequential access medium based at least in part on the write quality class. In some embodiments, the at least three classes of write quality may comprise a hard rewrite class for which rewrites are necessary to prevent data loss, a soft rewrite class for which rewrites are desirable but not necessary, and a no rewrite class for which no rewrite is needed or desired.

Selective hard and soft rewrites

Mechanisms are provided to receive encoded header information stored on a tape of a tape drive, wherein the encoded header information has been generated by: generating, for a plurality of tracks of the tape of the tape drive, a header information in a plurality of symbols, wherein the plurality of symbols is comprised of a first set of symbols and a second set of symbols, wherein the first set of symbols include identical information across all tracks of the plurality of tracks, and wherein the second set of symbols are configurable to include different information across all tracks of the plurality of tracks; and modifying, for writing to the tape of the tape drive, the first set of symbols of the plurality of tracks to include parity information corresponding to information included in the second set of symbols of the plurality of tracks. The received encoded header information is decoded.

Header decoding mechanism for tape storage

Managing metadata added to a file, a directory, or a symbolic link is provided. One or more pieces of metadata of a movement target are obtained. The movement target is at least one of a file, a directory, and a symbolic link. The movement target is to be moved from one file system to another file system within a plurality of file systems. Whether the one or more pieces of metadata are migratable to the other file system is determined based, at least in part, on metadata stored in the other file system. The one or more pieces of metadata are processed by (i) migrating a first piece of metadata that is determined to be migratable to the other file system and (ii) leaving a second piece of metadata in the one file system, wherein the second piece of metadata is determined to be non-migratable.

Information management

A methodology that enables, for example, tape drive operation at lower SNR and/or reduced rewrite area uses a first threshold T and a second threshold r for a rewrite condition. Codeword interleaves (CWIs) in a data set are written onto a plurality of simultaneously-written parallel tracks of a magnetic recording medium, read back and error correction decoded. A determination is made as to whether at least one of the Cor C' codewords in each decoded CWI contains more byte errors than the second threshold r of the rewrite condition. A number of CWIs in a rewrite buffer are according to the following criteria: b&#x2032;=b&#x2212;T when bis greater than the first threshold T, and b&#x2032;=0 when bis less than or equal to the first threshold T.

Magnetic tape device capable of selecting codeword rewrite based on determined threshold

Software for reclaiming a storage medium. The software determines that a first storage medium storing data in a linear tape file system (LTFS) format meets a predetermined condition indicating that the first storage medium should be reclaimed. Responsive to reading requested data from the first storage medium, and responsive to determining that the first storage medium meets the predetermined condition, the software writes the requested data to a second storage medium in the LTFS format. Subsequent to writing the requested data to the second storage medium, the software reconciles the first storage medium to delete expired data. Subsequent to reconciling the first storage medium, the software explicitly reclaims remaining data on the first storage medium to the second storage medium in the LTFS format.

Reclamation of storage medium

A method includes, in a tape apparatus system, receiving a request to write a file from a host, and, in response to the request, dividing sequentially received data of the file into two or more segments. Each of the two or more segments have a predetermined size. The method further includes sequentially writing a series of the two or more segments onto one or more tapes, and determining the predetermined size based on a capacity use efficiency of a plurality of other tapes and a time to copy when a spanning file, written by spanning on the one or more tapes, is copied to the plurality of other tapes. A corresponding computer program product and computer system are also disclosed.

Writing data spanning plurality of tape cartridges

Employing a virtual archive file (VAF) to improve access efficiency to files stored on sequential-access media. A rule is received for identifying a plurality of files existing on a sequential-access medium which are to be accessed as a single archive file. A virtual archive file is created on a random-access medium to represent the plurality of files. Content metadata of the virtual archive file, which contents metadata includes identifying information for each file in the plurality of files, is dynamically generated based on the rule. In response to an instruction to perform a read-only operation on the virtual archive file, the read-only operation is performed on the plurality of files as a whole.

Reducing time to read many files from tape

A computer-implemented metadata processing method and a system includes writing metadata to or reading metadata from a storage medium in which an index that contains metadata of each of one or more pieces of data is stored. The method and system include determining, in response to a processing request, which includes a write request or a read request, when to communicate with a storage area outside the index. At least a portion of content of the metadata relating to the processing request is processed, and accessed, including storing or obtaining, in the index, location information indicating the storage area of the portion of content of the metadata.

Metadata storing technique

Embodiments of the present invention provide methods, systems, and computer program products for estimating mount time completion in file systems. In an embodiment, at a time of unmounting storage media, an index file is provided, which records information stored in the storage media. Information associated with a number of tags of the index file, the types of contents of the tags, and a size of the contents of an element are stored, in response to an unmounting operation of the storage media. A predicted time associated with loading the index file into the memory during a mounting operation of the storage media is calculated, based on the stored information.

Estimating mount time completion in file systems

A drive-implemented method according to one embodiment includes determining that unthreading of a tape is to be performed, and in response to the determination that the unthreading of the tape is to be performed, determining whether to write an index on the tape prior to unthreading the tape. In response to a determination to write the index on the tape, the index is written on the tape prior to unthreading the tape. The tape is then unthreaded. The drive-implemented method further includes receiving a write request after the unthreading, rethreading the tape, and writing data corresponding to the write request on the tape. The index stored on the tape prior to the unthreading is overwritten with the data corresponding to the write request.

Selective index writing prior to unthreading a magnetic recording tape

A method for writing a file from an application of a host onto a tape includes sequentially receiving records forming the file from the application, adding a predetermined number of segments of dummy data (dummy records) subsequently to the plurality of records forming the file such that the records of the file and records of a subsequent file are not included in the same data set, interposing the dummy records between a final record of the file and a head record of the subsequent (next) file, to thereby construct at least one data set that is adjacent to one data set and does not include the records of the file, and writing a data set including the records of the file, a data set (dummy data set) including the final record of the file and the dummy records, and a data set including the subsequent file, onto the tape.

Deleting files written on tape

A method for writing a plurality of files includes receiving data of the plurality of files requested to be written to a tape from an application of a host, dividing a group of the received plurality of files into segments with specified sizes, and writing a series of the plurality of respective segments of the group of the plurality of files in sequence in a specified order, the respective segments having the specified sizes, wherein when writing the segments in the specified order, a left end portion of the tape is positioned and respective top segments of the files are first collectively written thereto.

Writing files to a storage medium

Software for reclaiming a storage medium. The software receives a read request targeting data in a storage system. The software reads the targeted data from a first storage medium storing the targeted data. The software responds to the read request with the targeted data. Responsive to reading the targeted data from the first storage medium and responsive to determining that the first storage medium meets a predetermined condition, the software writes the targeted data to a second storage medium for reclamation. The software may also, subsequent to writing the targeted data to the second storage medium for reclamation, explicitly reclaim the data on the first storage medium to the second storage medium, wherein a time required for explicitly reclaiming is reduced due to the targeted data having already been written to the second storage medium.

Growing community of inventors

Urayasu, Japan

Masayuki Iwanaga