News Column

"Library Controller and Method for Controlling Library Device" in Patent Application Approval Process

July 22, 2014



By a News Reporter-Staff News Editor at Information Technology Newsweekly -- A patent application by the inventor Ochi, Yoshiaki (Kawasaki, JP), filed on October 1, 2013, was made available online on July 10, 2014, according to news reporting originating from Washington, D.C., by VerticalNews correspondents.

This patent application is assigned to Fujitsu Limited.

The following quote was obtained by the news editors from the background information supplied by the inventors: "A library device may be used in order to backup data stored on a medium such as a hard disk drive of a storage device. The library device writes data received from a host device onto a recording medium such as magnetic tape, according to write commands received from the host device.

"FIG. 1 illustrates an exemplary configuration of a library device. The library device 102 in FIG. 1 includes a controller 121, drives 122-1 to 122-4, an operating unit 123, and storage 124.

"The storage 124 is a storage shelf that stores multiple magnetic tapes. The drives 122-1 to 122-4 are tape drives that write data to magnetic tape and read data from magnetic tape. The drives 122-1 to 122-4 respectively include data buffers 133-1 to 133-4 for temporarily storing data.

"In the following description, the terms 'drive 122' and 'drives 122' will be used in some cases to refer to one or more of any of the drives 122-1 to 122-4.

"The operating unit 123 is a transport mechanism such as a robot, performing operations to retrieve and mount a magnetic tape from the storage 124 into a drive 122, and operations to demount and store a magnetic tape from a drive 122 in the storage 124.

"The controller 121 is connected to a host device 101 by a communication line 131, and connected to the drives 122-1 to 122-4 by communication lines 132-1 to 132-4, respectively. The communication line 131 is a serial optical channel link using optical fiber, for example, while the communication lines 132-1 to 132-4 are parallel or serial Small Computer System Interface (SCSI) lines, for example.

"The controller 121 communicates with the host device 101 via the communication line 131, and communicates with the drives 122-1 to 122-4 via the communication lines 132-1 to 132-4, respectively.

"FIG. 2 illustrates an example of a write process by the library device 102 in FIG. 1. The host device 101 transmits a write command WR1, including data D1, to the controller 121 (S211). The controller 121 writes the data D1 to the data buffer 133-1 of the drive 122-1 by converting the write command WR1 into a command for the drive, and transferring the converted command to the drive 122-1 (S212). The drive 122-1 transmits to the controller 121 a response indicating that writing to the data buffer 133-1 has finished (S213).

"In order to more quickly respond to the host device 101, the controller 121, upon receiving the response from the drive 122-1, transmits to the host device 101 a response indicating that writing to the magnetic tape 201 has finished (S214). After that, the drive 122-1 asynchronously writes the data D1 from the data buffer 133-1 to the magnetic tape 201 (S215). At this point, the drive 122-1 writes the data D1 at a beginning of tape (BOT) position within a range from the BOT to an end of tape (EOT) of the magnetic tape 201.

"With an asynchronous write, a response indicating that writing has finished is transmitted from the controller 121 to the host device 101 when the writing to the data buffer 133-1 is completed. In contrast, with a synchronous write, a response indicating that writing has finished is transmitted from the controller 121 to the host device 101 when the writing to the magnetic tape 201 is completed.

"Next, an example of a write process will be described with reference to FIGS. 3 to 9, for a case in which the controller 121 receives backup write commands WR1 to WR4 from the host device 101.

"First, upon receiving the write command WR1 (S301 in FIG. 3), the controller 121 writes the data D1 included in the write command WR1 to the data buffer 133-1 by transferring the write command WR1 to the drive 122-1 (S302). The drive 122-1 transmits to the controller 121 a response indicating that the writing of the data D1 has finished (S303), and the controller 121 transmits to the host device 101 a response indicating that the writing of the data D1 has finished (S304).

"Next, upon receiving the write command WR2 (S305), the controller 121 writes the data D2 included in the write command WR2 to the data buffer 133-1 by transferring the write command WR2 to the drive 122-1 (S306). The drive 122-1 transmits to the controller 121 a response indicating that the writing of the data D2 has finished (S307), and the controller 121 transmits to the host device 101 a response indicating that the writing of the data D2 has finished (S308).

"Next, upon receiving the write command WR3 (S309), the controller 121 writes the data D3 included in the write command WR3 to the data buffer 133-1 by transferring the write command WR3 to the drive 122-1 (S310). The drive 122-1 transmits to the controller 121 a response indicating that the writing of the data D3 has finished (S311), and the controller 121 transmits to the host device 101 a response indicating that the writing of the data D3 has finished (S312).

"Next, upon receiving the write command WR4 (S401 in FIG. 4), the controller 121 writes the data D4 included in the write command WR4 to the data buffer 133-1 by transferring the write command WR4 to the drive 122-1 (S402). The drive 122-1 transmits to the controller 121 a response indicating that the writing of the data D4 has finished (S403), and the controller 121 transmits to the host device 101 a response indicating that the writing of the data D4 has finished (S404).

"At this point, the data buffer 133-1 has become full, and consequently the drive 122-1 writes the leading data D1 stored in the data buffer 133-1 to the magnetic tape 201, and deletes the data D1 from the data buffer 133-1 (S405).

"While writing the data D1 to the magnetic tape 201, if the controller 121 receives from the host device 101 a command WFM to write a tape mark indicating a file marker (S511 in FIG. 5), the controller 121 transfers the command WFM to the drive 122-1 (S512). The drive 122-1 defers execution of the command WFM until all data stored in the data buffer 133-1 is written to the magnetic tape 201.

"If the writing of the data D1 finishes normally (S501), the drive 122-1 writes the data D2 stored in the data buffer 133-1 to the magnetic tape 201, and deletes the data D2 from the data buffer 133-1 (S601 in FIG. 6).

"If the writing of the data D2 finishes normally (S602), the drive 122-1 writes the data D3 stored in the data buffer 133-1 to the magnetic tape 201, and deletes the data D3 from the data buffer 133-1 (S701 in FIG. 7).

"If the writing of the data D3 finishes normally (S702), the drive 122-1 writes the data D4 stored in the data buffer 133-1 to the magnetic tape 201, and deletes the data D4 from the data buffer 133-1 (S801 in FIG. 8).

"If the writing of the data D4 finishes normally (S802), all of the data D1 to D4 stored in the data buffer 133-1 has been written to the magnetic tape 201, and the data buffer 133-1 becomes empty. Consequently, the drive 122-1 executes the deferred command WFM, and writes a tape mark 911 at a position after the data D4 on the magnetic tape 201 (S901 in FIG. 9).

"If the writing of the tape mark 911 finishes normally (S902), the drive 122-1 transmits to the controller 121 a response indicating that the writing of the tape mark 911 has finished (S903). The controller 121 transmits to the host device 101 a response indicating that the writing of the tape mark 911 has finished (S904).

"There also exists a magnetic tape control device including a main buffer that temporarily buffers write data transferred in units of blocks via an input/output bus, and an auxiliary buffer that receives and stores the write data temporarily buffered in the main buffer. When retrying the writing due to a write error in a magnetic tape device, the magnetic tape control device transfers write data stored in the auxiliary buffer to a cache buffer of the magnetic tape device, and causes the data to be written.

"A related technique is disclosed in, for example, Japanese Laid-open Patent Publication No. 6-175792.

"The library device of the related art described above has problems like the following.

"In the case where writing to magnetic tape fails due to a malfunction of the magnetic tape or a malfunction of a magnetic head in a drive, a dynamic device reconfiguration (DDR) process may be conducted. With a DDR process, the library device mounts the magnetic tape having a write failure into another drive, and continues writing data from the position where the writing failed in order to recover data.

"However, with a DDR process, the write data that has been transferred from the host device to a drive is transferred back to the host device as unwritten data, and once again transferred from the host device to another drive. For this reason, the transfer of unwritten data is time-consuming, while also increasing the load on the host device.

"Furthermore, due to recent advances in technology, the magnetic tape format in library devices is shifting from cartridge magnetic tape (CMT) to linear tape-open (LTO), with a corresponding increase in capacity of the data buffer inside drives. As the capacity of the data buffer increases, the size of unwritten data correspondingly increases. For this reason, the transfer of unwritten data takes more time, and the load on the host device becomes greater compared to the case of CMT.

"Note that these problems are not limited to the case of using magnetic tape as a recording medium, and also occur in the case of using other recording media."

In addition to the background information obtained for this patent application, VerticalNews journalists also obtained the inventor's summary information for this patent application: "According to an aspect of the present invention, provided is a library controller for controlling a library device including a first drive, a second drive, and an operating unit. The library controller includes a data storage and a processor. The processor is configured to receive a plurality of data from a host device. The processor is configured to write the received plurality of data to a first data buffer included in the first drive. The processor is configured to instruct, upon occurrence of a first write error, the operating unit to demount a recording medium from the first drive and mount the recording medium into the second drive. The first write error is an error occurred while the first drive is writing partial data from among the plurality of data stored in the first data buffer to the recording medium. The processor is configured to receive unwritten data including the partial data from the first drive to store the received unwritten data in the data storage. The unwritten data is data stored in the first data buffer and not yet written to the recording medium. The processor is configured to read the unwritten data stored in the data storage to write the read unwritten data to a second data buffer included in the second drive.

"The object and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the claims.

"It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention, as claimed.

BRIEF DESCRIPTION OF DRAWINGS

"FIG. 1 is a diagram illustrating an exemplary configuration of a library device of a related art;

"FIG. 2 is a diagram illustrating a first write process of a related art;

"FIG. 3 is a diagram illustrating a second write process of a related art;

"FIG. 4 is a diagram illustrating a second write process of a related art;

"FIG. 5 is a diagram illustrating a second write process of a related art;

"FIG. 6 is a diagram illustrating a second write process of a related art;

"FIG. 7 is a diagram illustrating a second write process of a related art;

"FIG. 8 is a diagram illustrating a second write process of a related art;

"FIG. 9 is a diagram illustrating a second write process of a related art;

"FIG. 10 is a diagram illustrating a first DDR process;

"FIG. 11 is a diagram illustrating a second DDR process;

"FIG. 12 is a diagram illustrating a second DDR process;

"FIG. 13 is a diagram illustrating a second DDR process;

"FIG. 14 is a diagram illustrating a second DDR process;

"FIG. 15 is a diagram illustrating a second DDR process;

"FIG. 16 is a diagram illustrating a second DDR process;

"FIG. 17 is a diagram illustrating a second DDR process;

"FIG. 18 is a diagram illustrating a second DDR process;

"FIG. 19 is a diagram illustrating an exemplary configuration of a library device according to an embodiment;

"FIG. 20 is a flowchart of write control;

"FIG. 21 is a diagram illustrating an exemplary hardware configuration of a controller;

"FIG. 22 is a diagram illustrating write control;

"FIG. 23 is a flowchart of write control in a case where a write error occurs;

"FIG. 24 is a flowchart of an interrupt process;

"FIG. 25 is a flowchart of a process conducted by a host device;

"FIG. 26 is a diagram illustrating a write control sequence in a case where a write error occurs; and

"FIG. 27 is a diagram illustrating a write control sequence in a case where a write error occurs."

URL and more information on this patent application, see: Ochi, Yoshiaki. Library Controller and Method for Controlling Library Device. Filed October 1, 2013 and posted July 10, 2014. Patent URL: http://appft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&u=%2Fnetahtml%2FPTO%2Fsearch-adv.html&r=497&p=10&f=G&l=50&d=PG01&S1=20140703.PD.&OS=PD/20140703&RS=PD/20140703

Keywords for this news article include: Fujitsu Limited, Information Technology, Information and Data Storage.

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Source: Information Technology Newsweekly


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