Variable speed recording method and apparatus for a magnetic tape drive
First Claim
1. A method for recording data at variable speeds onto a magnetic tape that is being transported across a rotating drum at a current tape transport speed, said rotating drum having a recording head disposed thereon to pass over said tape once per single rotation of said drum, said data being received from a host system and temporarily stored in a data buffer, said method comprising:
- monitoring a current buffer level of said data buffer, said current buffer level indicating an amount of data currently present in said data buffer;
determining a new tape transport speed based on said current buffer level; and
adjusting said current tape transport speed to said new tape transport speed;
wherein said current tape transport speed and said new tape transport speed are each non-zero.
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Accused Products
Abstract
A method and apparatus for varying track recording speed to maximize host-to-tape data transfer rates is presented. Variable data transfer rates of host systems and networks are accommodated by continually adjusting the tape speed to match the tape drive to the host'"'"'s actual transfer rate. jThe speed of the tape is adjusted according to both the level of data present in the tape drive data buffer and whether the current mode of the drive is write mode or read mode. In the preferred embodiment, when the tape speed is accelerated or decelerated while writing a number of data track pairs to tape, a predetermined number of dummy track pairs are first written to tape at the current speed. On the next write head phase after the speed is increased or decreased as appropriate while the read heads are over the track, a predetermined number of dummy track pairs followed by more data track pairs are written to the tape at the new speed.
21 Citations
32 Claims
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1. A method for recording data at variable speeds onto a magnetic tape that is being transported across a rotating drum at a current tape transport speed, said rotating drum having a recording head disposed thereon to pass over said tape once per single rotation of said drum, said data being received from a host system and temporarily stored in a data buffer, said method comprising:
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monitoring a current buffer level of said data buffer, said current buffer level indicating an amount of data currently present in said data buffer;
determining a new tape transport speed based on said current buffer level; and
adjusting said current tape transport speed to said new tape transport speed;
wherein said current tape transport speed and said new tape transport speed are each non-zero. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29)
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15. A method for recording data at variable speeds onto a magnetic tape that is being transported across a rotating drum at a first tape transport speed, said rotating drum having a recording head disposed thereon to pass over said tape once per single rotation of said drum, said data being received from a host system and temporarily stored in a data buffer, said method comprising:
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halting tape transport such that a current tape transport speed is reduced to zero;
monitoring a current buffer level of said data buffer, said current buffer level indicating an amount of data currently present in said data buffer;
determining a second tape transport speed based on said current buffer level, said second tape transport speed being non-zero; and
adjusting said current tape transport speed from zero to said second tape transport speed to commence tape transport.
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30. A reel tension controller for a tape transport mechanism, said tape transport mechanism comprising a capstan which controls tape transport, a supply reel and a takeup reel between which a magnetic tape is transported, comprising:
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a reel amplifier responsive to a reel amplifier input signal to adjust the tension between said capstan and said supply reel and said takeup reel;
a controller responsive to correct tension parameters, a supply reel radius signal, and a takeup reel radius signal, said controller generating said reel amplifier input signal based on said correct tension parameter, said supply reel radius signal and said takeup reel radius signal.
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31. A method for preventing the recording of a thin track on a magnetic medium by a magnetic tape drive, said magnetic tape drive comprising a tape transport mechanism comprising a supply reel, a takeup reel, a recording head, and a capstan which moves a magnetic tape between said supply reel and said takeup reel in a path across said recording head, said capstan comprising a capstan tachometer which maintains a capstan tach count proportional to a number of revolutions of said capstan that have occurred relative to a beginning-of-tape position of said magnetic tape in said drive, said method comprising the steps of:
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determining a reference position of a track based upon a current tape speed;
measuring a current position of said track based upon said current tach count of said capstan;
determining a current track spacing, said current track spacing comprising the distance between a first track and a second adjacent track;
calculating a current track spacing error from said reference position and said current position; and
if said current track spacing error is below an acceptable track spacing error threshold;
setting said reference position to said current position;
setting said current track spacing error to zero. - View Dependent Claims (32)
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Specification