TRANSPORT SPEED ADJUSTMENT DEVICE, TRANSPORT SPEED ADJUSTMENT METHOD AND TRANSPORT SPEED ADJUSTMENT PROGRAM FOR ADJUSTING TRANSPORT SPEED OF TAPE MEDIUM

• US 20110116185A1
• Filed: 07/03/2009
• Published: 05/19/2011
• Est. Priority Date: 07/08/2008
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: OISHI, Yutaka, KATAGIRI, Takashi, NAKAYAMA, Hirokazu
• Granted Patent: US 8,625,227 B2
• Time in Patent Office: Days
• US Class Current: 360/73.04
• CPC Class Codes: G11B 15/1875 adaptations for special effects or editing signal processing or indexing therefor G11B27/00
• CPC Class Codes: G11B 15/46 Controlling, regulating, or indicating speed dependent on position of tape in reserve, loop G11B15/56, G11B15/58
• CPC Class Codes: G11B 20/10527 Audio or video recording; Data buffering arrangements G11B20/12 - G11B20/18 take precedence
• CPC Class Codes: G11B 2020/10703 processing rate of the buffer, e.g. by accelerating the data output
• CPC Class Codes: G11B 2020/10981 Recording or reproducing data when the data rate or the relative speed between record carrier and transducer is variable
• CPC Class Codes: G11B 2220/90 Tape-like record carriers

Abstract

A tape drive capable of switching the transport speed of a tape medium among multilevel speeds calculates a data transfer rate from/to a host device, and selects an adjustment mode of the transport speed of the tape medium from a constant speed mode and a speed switch mode according to the calculated data transfer rate. The tape drive in the speed switch mode, pauses a data write or read operation to switch the transport speed of the tape medium while data is written at a first transport speed and when an available capacity of a buffer memory reaches a data volume to be received from the host device during switching of the transport speed and is read out at the first transport speed and when a data volume of a buffer memory reaches a data volume to be transmitted to the host device during switching of the transport speed.

Claims

1. A transport speed adjustment device for adjusting a transport speed of a tape medium, comprising:

receiving means for receiving data from a host device through a network;

a buffer memory for temporarily storing the received data therein;

transport means for transporting the tape medium in a longitudinal direction thereof at a transport speed selected from multilevel transport speeds at which transport means can transport the tape medium;

writing means for writing the data in the buffer memory into a track formed to extend in a transport direction of the tape medium;

transfer rate calculation means for calculating a first transfer rate which is a data transfer rate between the host device and the transport speed adjustment device;

mode selection means for selecting, from adjustment modes consisting of a speed switch mode and a constant speed mode, an adjustment mode corresponding to the calculated first transfer rate, by referring to a mode selection table in which such an adjustment mode more effective in reducing back hitches is defined in accordance with the first transfer rate, the transport speed being switched between a first transport speed and a second transport speed in the speed switch mode, the transport speed being fixed at the second transport speed in the constant speed mode, the first transport speed being a highest speed of one or more transport speeds at which the transport means can be caused to operate under a condition that a second transfer rate, which is a data transfer rate between the buffer memory and the tape medium, is lower than the first transfer rate, the second transport speed being one-level higher than the first transport speed;

transport speed setting means for causing the transport means to operate at the first transport speed at a beginning of data writing, in response to selection of the speed switch mode;

required time obtaining means for obtaining a time required to switch the transport speed of the tape medium from the first transport speed to the second transport speed, in response to the selection of the speed switch mode;

threshold calculation means for calculating, from the first transfer rate and a required time, a data volume expected to be received from the host device during switch of the transport speed, as a threshold;

monitoring means for monitoring an available data storage capacity of the buffer memory while data is written at the first transport speed in the speed switch mode, and outputting a first switch notice if the available capacity reaches the threshold; and

speed adjustment means for stopping movement of the writing means and causing the transport means to operate at the second transport speed, in response to the first switch notice.

2. The transport speed adjustment device according to claim 1, further comprising:

compression means for compressing the received data before the data is stored in the buffer memory, wherein

the transfer rate calculation means calculates V/T as the first transfer rate, from a data volume V stored in the buffer memory in a time span T.

3. The transport speed adjustment device according to claim 1, wherein

the monitoring means also monitors an available data storage capacity of the buffer memory while data is written at the second transport speed in the speed switch mode, and also outputs a second switch notice if the available capacity reaches an initial capacity of the buffer memory, and

the speed adjustment means also stops movement of the writing means and causes the transport means to operate at the first transport speed, in response to the second switch notice.

4. The transport speed adjustment device according to claim 1, wherein the required time includes:

a time required to pause transportation of the tape medium;

a time required to rewind the tape medium for positioning of the writing means; and

a time required to set the transport direction of the tape medium back to a normal transport direction and to switch the transport speed from the first transport speed to the second transport speed.

5. The transport speed adjustment device according to claim 1, further comprising:

a storage for storing therein a table in which each of the multilevel transport speeds at which the transport means can be caused to operate is associated with the second transfer rate, the second transfer rate being selected when the transport means is caused to operate at the transport speed, wherein

the transport speed setting means determines a transport speed at which the transport means is caused to operate, by referring to the table.

6. The transport speed adjustment device according to claim 5, further comprising:

management information adding means for adding management information to the data stored in the buffer memory, the management information being used for managing the data in the transport speed adjustment device; and

correction information adding means for adding error correction information to the data stored in the buffer memory, the error correction information being used for performing error correction on the data, wherein

as the second transfer rate, V/T is calculated from a data volume V firstly processed by both the management information adding means and the correction information adding means and then transmitted to the tape medium in a time span T.

7. A transport speed adjustment device for adjusting a transport speed of a tape medium, comprising:

transport means for transporting the tape medium in a longitudinal direction thereof at a transport speed selected from multilevel transport speeds at which transport means can transport the tape medium;

reading means for reading out data recorded in a track formed to extend in a transport direction of the tape medium;

a buffer memory for temporarily storing the read out data therein;

transmitting means for transmitting the data in the buffer memory to a host device through a network;

transfer rate calculation means for calculating a first transfer rate which is a data transfer rate between the host device and the transport speed adjustment device;

mode selection means for selecting, from adjustment modes consisting of a speed switch mode and a constant speed mode, an adjustment mode corresponding to the calculated first transfer rate, by referring to a mode selection table in which such an adjustment mode more effective in reducing back hitches is defined in accordance with the first transfer rate, the transport speed being switched between a first transport speed and a second transport speed in the speed switch mode, the transport speed being fixed at the second transport speed in the constant speed mode, the first transport speed being a highest speed of one or more transport speeds at which the transport means can be caused to operate under a condition that a second transfer rate, which is a data transfer rate between the buffer memory and the tape medium, is lower than the first transfer rate, the second transport speed being one-level higher than the first transport speed;

required time obtaining means for obtaining a time required to switch the transport speed of the tape medium from the first transport speed to the second transport speed, in response to the selection of the speed switch mode;

threshold calculation means for calculating, from the first transfer rate and the required time, a data volume expected to be transmitted to the host device during switch of the transport speed, as a threshold;

monitoring means for monitoring a data volume stored in the buffer memory while data is read out at the first transport speed in the speed switch mode, and outputting a first switch notice if the data volume reaches the threshold; and

speed adjustment means for stopping movement of the reading means and causing the transport means to operate at the second transport speed, in response to the first switch notice.

8. The transport speed adjustment device according to claim 7, further comprising:

decompression means for decompressing the data read out from the buffer memory before the data is transmitted to the host device, wherein

compressed data is recorded in the tape medium, and

the transfer rate calculation means calculates V/T as the first transfer rate, from a data volume V forwarded from the buffer memory to the decompression means in a time span T.

9. The transport speed adjustment device according to claim 7, wherein the required time includes:

a time required to pause transportation of the tape medium;

a time required to rewind the tape medium for positioning of the reading means; and

a time required to set the transport direction of the tape medium back to a normal transport direction and to switch the transport speed from the first transport speed to the second transport speed.

10. The transport speed adjustment device according to claim 7, further comprising:

transport speed setting means for causing the transport means to operate at the second transport speed at the beginning of data reading, wherein

the monitoring means also monitors a data volume stored in the buffer memory while data is read out at the second transport speed in the speed switch mode, and also outputs a second switch notice if the data volume reaches an initial capacity of the buffer memory, and

the speed adjustment means also stops movement of the reading means and causes the transport means to operate at the first transport speed, in response to the second switch notice.

11. The transport speed adjustment device according to claim 10, further comprising:

a storage for storing therein a table in which each of the multilevel transport speeds at which the transport means can be caused to operate is associated with the second transfer rate, the second transfer rate being selected when the transport means is caused to operate at the transport speed, wherein

the transport speed setting means determines a transport speed at which the transport means is caused to operate, by referring to the table.

12. The transport speed adjustment device according to claim 11, further comprising:

error correction means for performing error correction on the data stored in the buffer memory, wherein

as the second transfer rate stored in the table, V/T is calculated from a data volume V firstly read out from the tape medium to the buffer memory and then processed by the error correction means in a time span T.

13. A transport speed adjustment method to be employed in a tape drive capable of switching a transport speed of a tape medium among multilevel speeds, the method comprising the steps of:

receiving data from a host device through a network;

temporarily storing the received data in a buffer memory;

transporting the tape medium in a longitudinal direction thereof;

writing the data in the buffer memory into a track formed to extend in a transport direction of the tape medium;

calculating a first transfer rate, which is a data transfer rate between the host device and the tape drive;

selecting, from adjustment modes consisting of a speed switch mode and a constant speed mode, an adjustment mode corresponding to the calculated first transfer rate, by referring to a mode selection table in which such an adjustment mode more effective in reducing back hitches is defined in accordance with the first transfer rate, the transport speed being switched between a first transport speed and a second transport speed in the speed switch mode, the transport speed being fixed at the second transport speed in the constant speed mode, the first transport speed being a highest speed of one or more transport speeds at which the tape drive can be caused to operate under a condition that a second transfer rate, which is a data transfer rate between the buffer memory and the tape medium, is lower than the first transfer rate, the second transport speed being one-level higher than the first transport speed;

causing the tape drive to operate at the first transport speed at a beginning of data writing, in response to selection of the speed switch mode;

obtaining a time required to switch the transport speed of the tape medium from the first transport speed to the second transport speed, in response to the selection of the speed switch mode;

calculating, from the first transfer rate and the required time, a data volume expected to be received from the host device during switch of the transport speed, as a threshold;

monitoring whether or not an available data storage capacity of the buffer memory reaches the threshold while data is written at the first transport speed in the speed switch mode; and

stopping writing the data and switching the transport speed of the tape medium to the second transport speed, in response to a monitoring result that the available capacity reaches the threshold.

14. A transport speed adjustment method to be employed in a tape drive capable of switching a transport speed of a tape medium among multilevel speeds, the method comprising the steps of:

transporting the tape medium in a longitudinal direction thereof;

reading out data recorded in a track formed to extend in a transport direction of the tape medium;

temporarily storing the read out data in a buffer memory;

transmitting the data in the buffer memory to a host device through a network;

calculating a first transfer rate which is a data transfer rate between the host device and the tape drive;

selecting, from adjustment modes consisting of a speed switch mode and a constant speed mode, an adjustment mode corresponding to the calculated first transfer rate, by referring to a mode selection table in which such an adjustment mode more effective in reducing back hitches is defined in accordance with the first transfer rate, the transport speed being switched between a first transport speed and a second transport speed in the speed switch mode, the transport speed being fixed at the second transport speed in the constant speed mode, the first transport speed being a highest speed of one or more transport speeds at which the tape drive can be caused to operate under a condition that a second transfer rate, which is a data transfer rate between the buffer memory and the tape medium, is lower than the first transfer rate, the second transport speed being one-level higher than the first transport speed;

obtaining a time required to switch the transport speed of the tape medium from the first transport speed to the second transport speed, in response to the selection of the speed switch mode;

calculating, from the first transfer rate and the required time, a data volume expected to be transmitted to the host device during switch of the transport speed, as a threshold;

monitoring whether or not a data volume stored in the buffer memory reaches the threshold while data is read out at the first transport speed in the speed switch mode; and

stopping reading out the data and switching the transport speed of the tape medium to the second transport speed, in response to monitoring result that the data volume reaches the threshold.

15. A transport speed adjustment program to be executed on a tape drive capable of switching a transport speed of a tape medium among multilevel speeds, the transport speed adjustment program causing the tape drive to execute the steps of:

receiving data from a host device through a network;

temporarily storing the received data in a buffer memory;

transporting the tape medium in a longitudinal direction thereof;

writing the data in the buffer memory into a track formed to extend in a transport direction of the tape medium;

calculating a first transfer rate, which is a data transfer rate between the host device and the tape drive;

selecting, from adjustment modes consisting of a speed switch mode and a constant speed mode, an adjustment mode corresponding to the calculated first transfer rate, by referring to a mode selection table in which such an adjustment mode more effective in reducing back hitches is defined in accordance with the first transfer rate, the transport speed being switched between a first transport speed and a second transport speed in the speed switch mode, the transport speed being fixed at the second transport speed in the constant speed mode, the first transport speed being a highest speed of one or more transport speeds at which the tape drive can be caused to operate under a condition that a second transfer rate, which is a data transfer rate between the buffer memory and the tape medium, is lower than the first transfer rate, the second transport speed being one-level higher than the first transport speed;

causing the tape drive to operate at the first transport speed at a beginning of data writing, in response to selection of the speed switch mode;

obtaining a time required to switch the transport speed of the tape medium from the first transport speed to the second transport speed, in response to the selection of the speed switch mode;

calculating, from the first transfer rate and the required time, a data volume expected to be received from the host device during switch of the transport speed, as a threshold;

monitoring whether or not an available data storage capacity of the buffer memory reaches the threshold while data is written at the first transport speed in the speed switch mode; and

stopping writing the data and switching the transport speed of the tape medium to the second transport speed, in response to a monitoring result that the available capacity reaches the threshold.

16. A transport speed adjustment program to be executed on a tape drive capable of switching a transport speed of a tape medium among multilevel speeds, the transport speed adjustment program causing the tape drive to execute the steps of:

transporting the tape medium in a longitudinal direction thereof;

reading out data recorded in a track formed to extend in a transport direction of the tape medium;

temporarily storing the read out data in a buffer memory;

transmitting the data in the buffer memory to a host device through a network;

calculating a first transfer rate which is a data transfer rate between the host device and the tape drive;

selecting, from adjustment modes consisting of a speed switch mode and a constant speed mode, an adjustment mode corresponding to the calculated first transfer rate, by referring to a mode selection table in which such an adjustment mode more effective in reducing back hitches is defined in accordance with the first transfer rate, the transport speed being switched between a first transport speed and a second transport speed in the speed switch mode, the transport speed being fixed at the second transport speed in the constant speed mode, the first transport speed being a highest speed of one or more transport speeds at which the tape drive can be caused to operate under a condition that a second transfer rate, which is a data transfer rate between the buffer memory and the tape medium, is lower than the first transfer rate, the second transport speed being one-level higher than the first transport speed;

obtaining a time required to switch the transport speed of the tape medium from the first transport speed to the second transport speed, in response to the selection of the speed switch mode;

calculating, from the first transfer rate and the required time, a data volume expected to be transmitted to the host device during switch of the transport speed, as a threshold;

monitoring whether or not a data volume stored in the buffer memory reaches the threshold while data is read out at the first transport speed in the speed switch mode; and

stopping reading out the data and switching the transport speed of the tape medium to the second transport speed, in response to monitoring result that the data volume reaches the threshold.