Avoiding write to read interference during self-servowriting

Details Avoiding write to read interference during self-servowriting Avoiding write to read interference during self-servowriting

2001-03-20

2003-11-25

Hudspeth, David (Department: 2651)

Dynamic magnetic information storage or retrieval

Automatic control of a recorder mechanism

Controlling the head

Reexamination Certificate

active

06654196

ABSTRACT:

TECHNICAL FIELD
This invention relates, in general, to the writing of servopatterns on recording media using self-propagation, and in particular, to avoiding write to read interference during the self-servowriting.
BACKGROUND ART
Self-servowriting is an attractive mechanism for producing servopatterns on recording media, such as disk files, because it eliminates the need for costly positioning systems and can be performed outside of a clean room environment. Processes for self-propagation of both radial and timing patterns have been developed recently. For example, in U.S. Pat. No. 5,659,436, entitled “Radial Self-Propagation Pattern Generation for Disk File Servowriting”, issued Aug. 19, 1997, which is hereby incorporated herein by reference in its entirety, a capability is described for deriving a servo position signal that is used to control the location of the head while writing tracks. In this example, the servo position signal is derived from the readback amplitude of a single track written one step earlier.
In modern disk files, however, the read element of the head can be offset from the write element of the head by as much as several tracks. When the read to write offset gets large, it is desirable to use a combination of readback amplitudes from several tracks to provide the position signal for the servo. This is described in, for example, U.S. Pat. No. 5,757,574, entitled “Methods and Systems for Self-Servowriting Including Maintaining a Reference Level Within a Usable Dynamic Range”, issued May 26, 1998, and commonly assigned, U.S. patent application Ser. No. 09/583,832, entitled “Techniques for Multitrack Positioning and Controlling Error Growth in Self-Servowriting Systems”, filed May 31, 2000, (herein referred to as the Multitrack Application), both of which are hereby incorporated herein by reference in their entirety.
The servo position signal is used during the radial propagation process to control the head in order to write burst information in time slots within the disk. Typically, the disk is partitioned into a number of sectors, and each sector includes a small number of time slots that are dedicated to the radial propagation process. Within a revolution of the disk, burst information is written in one of the slots in each sector of a track. The slots are cycled through, with a given slot reused after a number of steps equal to the number of slots. If the number of slots is not large enough, a track being written will coincide with one of the slots being read. Electrical interference from writing will alter the readback signal which will disturb the servo positioning and cause an error in the position of the written track.
A further complication arises from the fact that the read to write offset generally varies with radial position due to the arc motion of the actuator and the difference in pivot to head distances of the read and write elements. In modern files, the offset can change by as much as five data cylinders or more in moving from the inner diameter (ID) to the outer diameter (OD) of the disk, and even larger variations are expected for future designs.
Thus, a need exists for a capability that avoids write to read interference with large offset heads. A further need exists for a capability that avoids interference for an offset that increases across the disk.
SUMMARY OF THE INVENTION
The shortcomings of the prior art are overcome and additional advantages are provided through the provision of a method of writing burst information on a recording medium having a plurality of tracks. The method includes, for instance, writing burst information within a plurality of slots of a first portion of tracks of the plurality of tracks, wherein the plurality of slots are chosen in a predefined order; and writing burst information within the plurality of slots of another portion of tracks of the plurality of tracks, wherein the plurality of slots are chosen using an order different than the predefined order.
In a further aspect of the present invention, a method of writing burst information on a recording medium having a plurality of tracks is provided. The method includes, for instance, selecting a slot on a track of the plurality of tracks to receive burst information, the selecting being unconcerned with a particular order for selecting slots; and writing burst information within the selected slot.
In yet a further aspect of the present invention, a method of writing burst information on a recording medium having a plurality of tracks is provided. The method includes, for instance, writing burst information within one or more slots of one or more tracks of the plurality of tracks; determining that if burst information is to be written in a slot of another track of the plurality of tracks that a write to read interference will occur; and selecting, in response to the determining, another slot of the another track to write the burst information.
In another aspect of the present invention, a method of writing burst information on a recording medium having a plurality of tracks is provided. The method includes, for instance, writing burst information within one slot of a track of the plurality of tracks; and writing burst information within another slot of a next track of the plurality of tracks, wherein the another slot is not in successive order of the one slot.
System and computer program products corresponding to the above-summarized methods are also described and claimed herein.
Advantageously, one or more capabilities of the present invention provide for varying the order in which slots are selected to receive burst information. This enables write to read interference, due to, for example, large offset heads, to be avoided. Further, it enables the write to read interference to be avoided using a small number of radial time slots. Yet further, one aspect of the present invention enables the avoidance of an interference for an offset that increases across the recording medium.
Additional features and advantages are realized through the techniques of the present invention. Other embodiments and aspects of the invention are described in detail herein and are considered a part of the claimed invention.


REFERENCES:
patent: 5659436 (1997-08-01), Yarmchuk et al.
patent: 5757574 (1998-05-01), Chainer et al.
patent: 5844742 (1998-12-01), Yarmchuk et al.
patent: 6078450 (2000-06-01), Chainer et al.
patent: 6469859 (2002-10-01), Chainer et al.

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