DE4419761A1 - Magnetic tape drive with relative longitudinal tracks - Google Patents

Abstract

A magnetic tape data recording system with longitudinal tracks 200, 202 having increased track density while using low cost head actuators and unformatted tapes. The formatting drive writes track location markers 214, for all tracks. Track location markers enable relative track positioning which in turn enables the formatting drive to use less precise head positioning relative to absolute track positioning. When formatting the tape, the first track locator is written relative to the tape edge and subsequent track locators are written at positions relative to their adjacent track locators. <IMAGE>

Description

This invention relates generally to magnetic Recording devices and in particular on tape drives longitudinal tracks for data recording.

For inexpensive magnetic tapes used for data recording used, includes a conventional format longitudinal nal tracks written by drives that a movable magnetic head with a read / write gap that is gradually moved from track to track. In space Common is the determination of each track position on devices with longitudinal track an absolute track. The determination an absolute track position simplifies tape replacement between drives and random access to the Traces. Any drive can have its magnetic head on any Move the track gradually without looking for the track have to.

Fig. 1 (prior art) illustrates the QIC-80 standard, an example of a longitudinal track format that is conventionally used for magnetic data tapes in the personal computer industry. Further information regarding the format shown in Fig. 1 can be found in "Flexible Disk Controller Compatible Recording Format for Information Interchange" available from Quarter-Inch Cartridge Drive Standards, Inc., 311 East Carillo Street, Santa Barbara, CA. 93101. Magnetic data tapes that are compatible with QIC formats are formatted by drives in a manner similar to formatting floppy disks and hard drives. The tracks are written to blank tapes by the drives. The tracks are logically formatted into hierarchical levels of addressable data blocks. The smallest addressable unit is a sector, with each sector having an address and other parent information that is recorded once during formatting and a data field that can be rewritten many times. Once a track is formatted, the location of the track is determined for any subsequent data recording. As shown in Fig. 1, the QIC-80 standard determines 28 tracks on a tape that is 6.35 mm (0.250 inches) wide. Section 4.1.1 of the standard determines the location of the center line of each track relative to a location pointer of a recorded track. All even-numbered tracks (forward direction) are determined as absolute distances from a first track location pointer 13 , which is aligned with track 0 ( 104 ). All odd-numbered tracks (backward direction) are determined as absolute distances from a second track location pointer 103 aligned with track 3 ( 106 ). The track centerlines are spaced 0.2159 mm (0.0085 inches), with track position tolerances of + 0.0254 mm, -0.0305 mm (+ 0.0010 inches, -0.0012 inches).

For QIC-80 compatible tapes, the track position pointers 100 , 102 are written by the drive that formats the tape. The position indicators 100 , 102 are fixed frequency signals (7.35 K flux reversals per inch) and are therefore referred to as a reference burst. The tape shifts its position slightly when the direction is reversed. Therefore there are two separate reference bursts, one for each band direction. There is a gap between the reference bursts to ensure that a head read gap cannot bridge the two reference bursts and read a partial signal from each. The positional accuracy of the reference bursts is determined relative to the overall tape centerline with a tolerance of +/- 0.0381 mm (+/- 0.0015 inches). The position of the tape centerline is typically determined mechanically relative to the edges of the tape, which in turn is determined by moving the magnetic head to mechanical stoppers that are precisely positioned relative to tape edge guides.

Have tape drives that are compatible with the QIC-80 format typically a stepper motor head actuator that is driven so that several steps of the motor are required to cross a track on the tape. A commercially available drive with a stepped motor and a lead screw assembly requires e.g. B. 30 steps the stepper motor around the head by 0.2159 mm (0.0085 inches) to move from one track to the next. If a drive is driven, or if a tape is inserted, the Head position initially by adjusting the head reading gap position to the center of the corresponding reference burst calibrated. All subsequent head movements become ty typically by moving the head gradually actuator stepper motor by the integer number of Steps per level (30 in the example above) times the required number of tracks using an open Control loop performed. After every QIC-80 drive Every QIC-80 drive must be able to format tracks Have head placement mechanism capable of traces absolutely with the accuracy described above locate.

The magnetic medium is due to temperature and Moisture changes from dimensional changes set. The head assembly mechanisms have their own ge Limitations of accuracy, which are determined by a calibration accuracy, non-linearities and wear further ver get worse. Moves as described above the band position is unchanged with the direction of movement avoidable. Dimensional changes in the media and various mechanical inaccuracies fundamentally limit the Track density. It is e.g. B. a hypothetical track density of ten times the QIC-80 standard (280 tracks instead of 28)  accepted. The mechanical accuracy that is required is about 140 hypothetical tracks with an absolute posi tion tolerance of +/- 0.0025 mm (+/- 0.0001 inches) relative Arranging to a reference burst would be a much more expensive one Head assembly system than the current low-cost Require stepper motor and lead screw assemblies. Dimensional changes of the media and mechanical un Accuracies can be achieved in part by creating a factory formatted tapes with embedded servo information in the traces (between the sectors) can be compensated. A an alternative solution is to leave the factory-written track to provide position points for each track. Every solution increases the cost of the product. Embedded help information require a real-time head arrangement with a closed rule loop, which increases the cost of the drive. A factory formatting or factory marking of track positions increases the cost of magnetic media. A factory format marking or factory marking of track positions multiple products require, each on a difference formatted although the unformatted tapes are identical are table. There is a need for tape drive systems with increased track density, the cheap head arrangement systems and use raw tapes.

It is the object of the present invention, a tape drive system to create an increased track density has unformatted tapes and inexpensive Head arrangement systems are used.

This task is followed by a data recording system Claim 1 and by a method for arranging data tracks on a magnetic tape according to claim 4 solved.

The present invention provides magnetic tape data drawing system with increased track density, being a relative inaccurate (inexpensive) head assembly control and emptiness (unformatted) tapes are used. Every track becomes one zeln by position markers by the drive that the  Tape formatted, recorded, localized. The Drive formatting the tape arranges each track relatively to an adjacent track with an accuracy that through the own accuracy of the head position actuator is determined. As a result, the absolute trace can become significantly differentiate position from drive to drive. If tapes are read or formatted again after formatting Compatible drives must be written to the track posi Use the marker to locate each track.

Preferred embodiments of the present invention are described below with reference to the accompanying Drawings explained in more detail. Show it

FIG. 1 is a plan view illustration of a magnetic tape showing the track format, the default is determined by the QIC 80;

Fig. 2 is a top plan view of a magnetic tape showing the track arrangement in accordance with the present invention;

Fig. 3 is a plan view of a magnetic tape with an alternative embodiment of the track marker and

Fig. 4 is a flowchart of the method of the relative arrangement of markers and tracks.

The primary object of the present invention is one increased track density while inexpensive head actuators and unformatted tapes are used. After unforma tapes are used, the preferred solution is Solution for the change problem for the formatting drive in writing track position markers on all tracks. Compatible drives must have head actuators, one Allow fine position adjustment (resolution), but they do do not have to have absolute position accuracy. Each  The drive that is not the formatting drive must have the Set the head position at least once for each track. The Track position markers preclude formatting drive an absolute track arrangement with high accuracy must have. The track position markers allow a relative Track arrangement, which in turn is the formatting drive enables compared to the absolute track arrangement we less accurate (and therefore less expensive) head assemblies use.

Tape drives typically become archival files Storage, for backup copies of hard drives, data exchange or other secondary storage applications used. In contrast to magnetic or optical dis Tape drives are typically not chained as devices used with random access. The data will be ty typically stored in long continuous blocks and recovered with the data transfer rate within of a block is important, and the access time to one particular block is not that important. For typical users For a tape drive, it is acceptable to set a track search, or set a position on a track in the Contrary to the direct gradual move on to one Track using an open control loop. That is why it is at typical data tape applications not necessary, random Lane changes with an open control loop without renewed Ka calibration of the track position.

For devices with random access, the magnetic me dium typically formatted in logical blocks, and data are done in separate operations after formatting wrote. The data transfer rate during a tape run work for archival data storage, he follows both formatting and writing Da during the same operation. A trace can be made during an operation to be "written" what the writing of the Formatting data includes, and the track can be used during an operation that is only based on  updating the data fields is limited. That's why means the term "format" in this description the first time a track is written and not necessarily a separate operation.

Fig. 2 illustrates an embodiment of a tape format with reference markers that are written by the formatting drive ge. Figure 2 illustrates 6 tracks numbered 0 through 5. As in Fig. 1, even-numbered tracks are written in one direction in Fig. 2, and odd-numbered tracks are written in the opposite direction. In FIG. 2, a reference burst 214 , 216 is written near the beginning of the tape (BOT = beginning of tape) 212 during the formatting of each further even-numbered track. In the vicinity of the end of the tape (EOT = End of Tape) 232 , a reference burst 234 , 236 is written for each further odd-numbered track. Each reference burst 214 , 216 , 234 , 236 has a centerline 218 , 222 , 238 , 242 that is aligned with the centerline of the corresponding track 200 , 204 , 234 , 236 . The reference bursts 214 , 216 , 234 , 236 are preferably arranged at least at each end of the band, as shown. Additional copies can also be located within the tracks at logical "volume" boundaries (a fixed number of sectors) to improve track access time. Tracks without a reference burst 202 , 208 have a center line halfway between two reference bursts. After formatting, a drive that reads or rewrites a tape as formatted in Fig. 2 must move the appropriate track by moving the tape to one end, gradually moving the head over the reference bursts 214 , 216 , 234 , 236 , as the tape moves near one end, place the head either in the middle of a reference burst 218 , 222 , 238 , 242 or midway between two reference bursts 220 , 240 as appropriate , to adjust. In typical operation, the drive runs from end to end in a serpentine pattern so that the time it takes to find a track position at each end of the tape adds little overhead to the overall transfer time.

If the reference bursts 214 , 216 , 234 , 236 were located on each track, a read head bridging two adjacent bursts would pick up some signals from each of the two bursts. Therefore the edges of the reference bursts could not be determined. The arrangement of a reference burst on every next but one track ensures that a magnetic head that reads the reference bursts generates distinguishable maximum and minimum signal amplitude levels for determining the reference burst edges and center lines. In general, it is easier to detect the edges of the reference bursts than to detect the center line. Therefore, a drive that reads a tape after formatting, e.g. B. find a center line 218 halfway between the reference burst edges 224 and 226 , a center line 220 halfway between the reference burst edges 226 and 228 , and so on. The reference bursts 214 , 216 , 234 , 236 can be a fixed frequency or any distinguishable digital pattern.

In Fig. 2, the track centerline position for the first track 200 relative to the tape edge guides can be determined in any of several ways that are well known and are currently used by drives to find reference bursts. The magnetic head can e.g. B. to mechanical stoppers, mechanical switches or light beam sensors, the stoppers, switches or sensors being arranged precisely relative to the strip edge guides. Alternatively, the head can be moved stepwise across the width of the tape as it writes to form a temporary "track" diagonally across the track. Then the transient diagonal track is read as the head is moved incrementally across the width of the tape again. The band edges are then detected by observing when the signal disappears. However, for all tracks except the first track 200 , the track centerline position is determined by the accuracy of the head position actuator of the formatting drive. That is, the formatting drive simply takes the appropriate integer number of steps per level. Track 1 206 may be spaced a gap between track 206 and track 0 200 to accommodate a position shift upon reversing direction, but track 1 206 is still located relative to track 0 200 and not at an absolute position. A subsequent read or write drive that uses a tape after formatting may have a slightly different amount of head movement for the same number of steps, or a subsequent drive may have a completely different drive ratio. To compensate for this, the subsequent read or write drive must find the centerline of each track as described above. In particular for tapes formatted as in FIG. 2, the track centerline positions are not determined by absolute positional accuracy relative to the tape edges or to an overall tape centerline.

FIG. 3 shows an alternative exemplary embodiment of the track position marker. In FIG. 3, the tracks 200-210 with their center lines 218-224 , 238-242 are the same as those shown in FIG. 2. The track position markers 300-322 are reference bursts adjacent to each other and with edges on each side of the track centerlines (e.g. 326 and 328 ). A magnetic head reading gap is centered across a track center line by adjusting the head position until identical signal amplitudes are received from successive marks. To zen tren a reading gap on the center line 218 , a head position z. B. set until a signal amplitude of burst 300 is identical to a signal amplitude of burst 302 (and 304 and 306 ). Similarly, to center a read gap on centerline 220 , the head position is adjusted so that the signal amplitudes of bursts 300 , 310 , 304 and 312 are equal. In the opposite direction, a read gap is centered on the center line 238 by equalizing the signal amplitudes of the bursts 316 , 318 , 320 and 322 . Only a few reference bursts 300-322 are shown. There are as many consecutive reference bursts as necessary to allow the head position control system to approach a track centerline before reading the general track information.

A drive that formats a tape as shown in Fig. 3 must first find the center of the tape from the edge of the tape information as described above. Then z. B. the reference bursts such. For example, bursts 302 and 306 are written. Then the head is moved gradually by half a track spacing to form the track 0 200 . After returning to BOT 212 , the head is incrementally moved half a track pitch to write bursts 300 and 304 , and then another track pitch to format track 2 202 . A gap 324 between the burst pairs provides displacement direction information to the head assembly mechanism. For the center line 280 , the head placement algorithm knows e.g. For example, the first burst after a gap 324 (burst 304 ) in the forward direction is near the center line 218 relative to the total track centerline, and the second burst after the gap 324 (burst 306 ) relative to the total track centerline from the centerline 218 is removed.

If a predetermined number of tracks is desired, a tape formatted as in Fig. 2 or 3 may have a predetermined number of tracks. The predetermined number must be based on a worst case (maximum) track width. If maximum tape capacity is desired, a formatting drive can maximize tape capacity simply by writing tracks until it reaches a tape edge. A drive with a relatively narrow track width can have more tracks than the predetermined number determined by a worst case constraint.

Figure 4 is a flow chart illustrating the process of relative placement of track position markers during formatting. At step 400 , the process is initialized by placing the innermost marker and the associated track relative to one or both band edges (e.g., Fig. 2, marker 214 and track 200 ). At steps 402 and 404 , the marker (s) and the associated track are written. At step 406 , the head is moved relative to the previously written markers. If maximum tape capacity is desired (step 408 ), new tracks are written until the edge of the tape is reached (step 410 ). If a predetermined number of tracks is desired, new tracks are written until a predetermined number of tracks are reached (step 414 ).

Other track position marker embodiments can be used be applied. The important parameters are: (a) the run work that formats the tape must also track Write position markers, and (b) all compatible runs plants must have head position control systems with adequate Have resolution around a head read or write gap center each track center line. The resulting front Part is that a high track density with empty (un formatted) tapes and without the requirement of a exact absolute head position control is obtained.

Claims (7)

1. Data recording system, with:
a magnetic tape with a first and a second tape edge;
a drive device for formatting the magnetic tape, the formatting including writing the following: a plurality of track pointers ( 214 , 216 , 234 , 236 ; 300-322 ), including a first track pointer;
a plurality of data tracks ( 200-210 );
wherein the first track pointer is arranged relative to at least one of the band edges;
each track pointer other than the first track pointer being located only relative to the location of an adjacent track pointer already written; and
wherein each data track is only arranged relative to at least one track pointer. 2. The data recording system of claim 1, further comprising:
each data track has a track centerline ( 218-222 , 238-242 );
each track pointer includes at least one marker ( 214 , 216 , 234 , 236 );
each marker ( 214 , 216 , 234 , 236 ) has two marker edges ( 224-230 ); and
each track center line ( 218-222 ; 238-242 ) is located halfway between two marker edges ( 224-230 ). 3. A data recording system according to claim 1, further comprising:
each data track has a track centerline ( 218-222 ; 238-242 );
each track pointers comprises a plurality of markers (300-322);
each marker of the plurality of markers ( 300-322 ) has a first marker edge ( 320 ) and a second marker edge ( 328 ); and
each track center line ( 218-222 ; 238-242 ) is aligned with at least one first marker edge ( 320 ) and is aligned with at least one second marker edge ( 328 ). 4. A method for arranging data tracks on a magnetic tape, the magnetic tape having a first tape edge, the method comprising the following steps:

• a) writing one or more track position markers, which are arranged relative to at least one of the tape edges ( 400 );
• b) writing a data track that is positioned relative to the track position markers from step a ( 402 );
• c) if this is the first time step c has been carried out,
• Writing one or more track position markers arranged relative to the track position markers written in step a;
  if this is not the first time step c has been performed,
  Writing one or more track position markers relative to adjacent track position markers that were written when step c was performed the previous time;
• d) writing a data track which is positioned relative to the track position markers from step c;
• e) repeating steps c and d.

5. The method of claim 4, wherein step e further comprises repeating steps c and d until a position of the track position markers in step c is at a tape edge ( 410 ). 6. The method of claim 4, wherein step e further comprises repeating steps c and d until a predetermined number of data tracks have been written ( 414 ).