International Business Machines Corporation

Hironobu Nagura

Takashi Katagiri

Yutaka Oishi

Hirokazu Nakayama

Hiroshi Itagaki

Kazuhiro Ozeki

Tohru Hasegawa

Glen Alan Jaquette

Atsushi Abe

Terue Watanabe

Paul Merrill Greco

Tetsuya Tamura

Toshiyuki Shiratori

Masayuki Demura

Tsuyoshi Miyamura

Keisuke Tanaka

Setsuko Masuda

Satoshi Tohji

Katsumi Yoshimura

Junta Watanabe

Toshimi Ataku

Akio Nakamura

Atsush Abe

A computer data storage system receives a plurality of data units from a host computer. The system stores the data units in a buffer memory. The system generates a plurality of data segments comprising a plurality of subsets of the plurality of data units. The system receives a plurality of dataset information tables (DSITs) corresponding to the plurality of data segments. The system appends the plurality of DSITs to the respectively corresponding plurality of data segments, to create a plurality of datasets stored in the buffer memory. The system determines a number of datasets stored in the buffer memory, exceeds a threshold value. And in response to determining the number of datasets, of the plurality of datasets stored in the buffer memory, exceeds the threshold value, the system stops the appending the plurality of DSITs to the respectively corresponding plurality of data segments.

Compensation for expansion and contraction across the width of a magnetic tape

In an approach to HRTD recovery by writing the HRTD in a null data set, responsive to receiving a request to write a data set to a magnetic tape, a lead data set of a current wrap of a plurality of wraps of the magnetic tape is written, wherein the lead data set of the current wrap includes a current wrap HRTD that contains one or more directory records for each wrap of the plurality of wraps from a lead wrap of the plurality of wraps through a first prior wrap of the plurality of wraps, and further wherein the first prior wrap immediately precedes the current wrap.

High resolution tape directory recovery by writing a null data set

When a WORM cartridge is formatted for Tape File System (LTFS) in advance, such as prior to shipment, Linear Tape File System Library Edition (LTFS LE) is expanded by software to reduce consumption of the index partition and to support elimination of the appending of unnecessary data. More specifically, instead of recording metadata in the index partition during normal unmounting, the metadata is recorded in separate local storage such as on hard disk drive (HDD), and the index partition is updated only when the cartridge is ejected from the library. In this way, the present invention is able to significantly reduce the frequency of index partition updates. Because an update occurs only when the user intentionally ejects a cartridge, overflow of the index partition before overflow of the data partition can be prevented.

Support for worm cartridges realized by linear tape file system (LTFS)

Support for WORM cartridges realized by linear tape file system (LTFS)

Provided are a storage device, method, and program for controlling a tape speed to manage a tape drive buffer. A tape speed is increased from a current tape speed to a target tape speed on a predetermined speed-change timing to control the reading or writing of data between the buffer and the tape medium.

Controlling a tape speed to manage a tape drive buffer

Data of a target capacity calculated by a nominal capacity of a tape medium minus a data capacity lost due to execution of backhitchless writing is written to the tape medium. In a tape drive, a command processing unitreceives a synchronization command, and a buffer management unit passes data in a buffer to a channel input-output unit. Upon completion of writing the data to the tape, a backhitch determination unit determines whether a mode information storage unit stores information indicating that a high data rate mode is on, whether data of a target capacity can be written to the tape, and whether the written data can be read at a target read data rate. An operation signal output unit issues a command to execute backhitch in case these conditions are not satisfied.

Apparatus and method for controlling data writing to a tape medium

A method for evaluating data transfer performance within a data recording apparatus is disclosed. The data recording apparatus includes a buffer and a recording medium. Initially, a Pause time P when data transfer between the buffer and a host being stopped temporarily is measured. Then, an ideal Pause time Y is determined. Next, a determination is made whether or not the Pause time P exceeds a sum of the ideal Pause time Y and an allowance a. If the Pause time P exceeds a sum of the ideal Pause time Y and the allowance a, a warning signal is sent to the host.

Method and apparatus for evaluating performance on host data transfer within a tape drive

A write/read control method for recording at least one datum on a magnetic tape within a predetermined distance is provided. The method includes sequentially accumulating a plurality of blocks of data of variable length in a buffer divided into fixed length segments and writing the contents of each segment to the tape. If the segment contains at least one block of data, the data is written to the tape as a dataset and if the segment does not contain any data, then a null dataset is written to the tape within the predetermined distance. The predetermined distance may vary depending upon the format of a tape drive embodying the method. In response to a request to read a block of data, reading at least one dataset that includes the requested block of data from the tape to segments in the buffer, and reading the requested block of data for invalidating data transfer of a null dataset in the segment. By invalidating the transfer of a null dataset, blocks of data separated by the null dataset can be reconstructed.

Method of controlling write and read of data for tape recording apparatus

Backspacing over data to overwrite the data as recorded on magnetic tape is provided logically, rather than by causing a magnetic tape to drive to backhitch. The data is written to the magnetic tape as it was before it was logically changed in order to insure that the data is preserved on tape. Recovery of the data is from a succeeding data set which logically invalidates the original data by a superseding identifier. Control logic arranges data transactions for writing to magnetic tape as data sets; and, in response to backspace and overwrite commands, or when transactions are accumulated into a succeeding data set, rewrites the original transaction adjusted in accordance with the commands as a superseding data set downstream from the original transaction, logically invalidating the original transaction by setting a superseding identifier in the superseding data set(s).

Writing to magnetic tape with backhitchless backspacing and data set invalidation

Special fields for error recovery are provided in data set information tables of data sets written with synchronized transactions. If a transaction only partially fills a data set, that data set is rewritten in a succeeding data set, appending the next transaction. A moving access point in the table identifies the appended transaction, allowing the rewritten transaction to be skipped during read recovery. The table provides recovery trails by providing a thread to tie the data sets together, the status of the data set, and pointers, such as identifying the wrap of the immediately succeeding data set.

Data set information for recovery of synchronized data on magnetic tape

A method and apparatus for detecting and correcting errors and erasures in product-coded data arrays by iterative syndrome processing array data in row major order and column major order. A first dense map is formed for classifying each row containing location indicia of random errors, their correction patterns, and pointers to rows containing erasure errors. This map is used to effectuate row array random error corrections in place in memory. A second dense map is formed of location indicia and correction patterns for each pair adjacent position within a column containing erasure errors as indexed by a counterpart row pointer. The second map is used to effectuate column array erasure corrections and random error corrections in place in memory.

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Kawasaki, Japan

Hironobu Nagura