Transport speed adjustment device, transport speed adjustment method and transport speed adjustment program for adjusting transport speed of tape medium

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

• transport means for rotating the tape medium to transport a portion of 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 a first range of transfer rates associated with the speed switch mode and a second range of transfer rates associated with the constant speed mode, wherein when the first transfer rate falls within the first range of transfer rates and the mode selection means selects the speed switch mode, the transport speed is switched between a first transport speed and a second transport speed in the speed switch mode by correspondingly increasing or decreasing the rotation of the tape medium, and wherein the first transfer rate falls within the second range of transfer rates and the mode selection means selects the constant speed mode, the transport speed is 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.

A transport speed adjustment computer program product to be executed on a tape drive capable of switching a transport speed of a tape medium among multilevel speeds, the transport speed adjustment computer program product comprising a non-transitory computer-readable storage medium having computer-readable program code portions stored therein, the computer-readable code portions comprising:

• computer-readable code for receiving data from a host device through a network;
• computer-readable code for temporarily storing the received data in a buffer memory;
• computer-readable code for rotating the tape medium to thereby transport the tape medium in a longitudinal direction thereof at a transport speed;
• computer-readable code for writing the data in the buffer memory into a track formed to extend in a transport direction of the tape medium;
• computer-readable code for calculating a first transfer rate, which is a data transfer rate between the host device and the tape drive;
• computer-readable code 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 a first range of transfer rates associated with the speed switch mode and a second range of transfer rates associated with the constant speed mode, wherein when the first transfer rate falls within the first range of transfer rates and the speed switch mode is selected, the transport speed is switched between a first transport speed and a second transport speed in the speed switch mode by correspondingly increasing or decreasing the rotation of the tape medium, wherein when the first transfer rate falls within the second range of transfer rates and the constant speed mode is selected, the transport speed is 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;
• computer-readable code for 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;
• computer-readable code 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;
• computer-readable code for 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;
• computer-readable code for 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
• computer-readable code for 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.

A transport speed adjustment computer program product to be executed on a tape drive capable of switching a transport speed of a tape medium among multilevel speeds, the transport speed adjustment computer program product comprising a computer-readable storage medium having computer-readable program code portions stored therein the computer-readable code portions comprising:

• computer-readable code for rotating the tape medium to transport a portion of the tape medium in a longitudinal direction thereof at the transport speed;
• computer-readable code for reading out data recorded in a track formed to extend in a transport direction of the tape medium;
• computer-readable code for temporarily storing the read out data in a buffer memory;
• computer-readable code for transmitting the data in the buffer memory to a host device through a network;
• computer-readable code for calculating a first transfer rate which is a data transfer rate between the host device and the tape drive;
• computer-readable code 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 a first range of transfer rates associated with the speed switch mode and a second range of transfer rates associated with the constant speed mode, wherein when the first transfer rate falls within the first range of transfer rates and the speed switch mode is selected, the transport speed of the tape medium is switched between a first transport speed and a second transport speed in the speed switch mode by correspondingly increasing or decreasing the rotation of the tape medium, wherein when the first transfer rate falls within the second range of transfer rates and the constant switch mode is selected, the transport speed is 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;
• computer-readable code 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;
• computer-readable code 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;
• computer-readable code for 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
• computer-readable code for 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.