US 5,844,920 A · Thermal asperity compensation using multiple sync marks for retroactive and split segment data synchronization in a magnetic disk storage system

Abstract

A magnetic disk storage system is disclosed wherein byte synchronization to sector data is achieved even when noise in the read channel, due for instance to a thermal asperity (TA), corrupts the primary preamble and/or sync mark fields or causes a loss of frequency or phase lock. The data sector format is modified to comprise at least one secondary sync mark in addition to the conventional primary sync mark recorded at the beginning of the data field. In this manner, when the primary sync mark becomes undetectable due to errors, or when byte synchronization is lost, the storage system can still synchronize to the data sector using the secondary sync mark. The secondary sync mark is preferably spaced apart from the primary sync mark with either a gap (no data) or user data inserted inbetween. In the latter embodiment, two methods are employed to recover user data inbetween the primary and secondary sync marks when the primary sync mark is undetectable: on-the-fly erasure pointer error correction, and buffering to facilitate retroactive synchronization. The secondary sync mark may optionally include a secondary preamble to facilitate phase locking to the data when the primary preamble is corrupted by errors. The present invention also provides "split segment" resynchronization for synchronizing a first section of data using a first mark, and retroactively synchronizing a second section of data using a following sync mark when synchronization is lost.

Claims34

Dependent claims

An apparatus for reading data recorded on a magnetic disk storage medium, wherein the disk storage medium comprises a plurality of concentric data tracks;

each data track comprises one or more data sectors;
and at least one data sector comprises a data field, a primary sync mark located at the beginning of the data field for initial synchronization, and at least one secondary sync mark located a predetermined number of datum after the primary sync mark within the data field for synchronizing to the data field;
the apparatus comprising:
(a) an input connected to receive a sequence of detected datum representing a data sector recorded on the magnetic disk storage medium;
(b) a sync mark detector, responsive to the sequence of detected datum, for detecting the primary sync mark, wherein when the primary sync mark is undetectable due to errors in the sequence of detected datum, the sync mark detector detects the secondary sync mark;
and
(c) a sync controller for synchronizing a first section of the data field following the primary sync mark using the primary sync mark, and for retroactively synchronizing a second section of the data field preceding the secondary sync mark using the secondary sync mark.

4 more elements

An apparatus for reading data recorded on a magnetic disk storage medium, wherein the disk storage medium comprises a plurality of concentric data tracks;

each data track comprises one or more data sectors;
and at least one data sector comprises a data field, a primary sync mark preceding the data field and at least one secondary sync mark embedded within the data field for synchronizing to the data field;
the apparatus comprising:
(a) a sampling device for sampling an analog read signal emanating from a read head positioned over the magnetic medium and generating a sequence of discrete time sample values;
(b) timing recovery for extracting timing information from the sequence of sample values;
(c) a discrete time sequence detector for detecting a bit sequence from the sequence of sample values;
(d) a sync mark detector, responsive to the sequence of discrete time sample values, for detecting the primary sync mark, wherein when the primary sync mark is undetectable due to errors, the sync mark detector detects the secondary sync mark;
(e) a sync buffer for storing the detected datum as it is received;
and
(f) a sync controller for synchronizing a first section of the data field following the primary sync mark using the primary sync mark, and for retroactively synchronizing a second section of the data field preceding the secondary sync mark using the secondary sync mark.

7 more elements

An apparatus for reading data recorded on a magnetic disk storage medium, wherein the disk storage medium comprises a plurality of concentric data tracks;

each data track comprises one or more data sectors;
and at least one data sector comprises a data field, a primary sync mark preceding the data field and at least one secondary sync mark embedded within the data field for synchronizing to the data field;
the apparatus comprising:
(a) a sampling device for sampling an analog read signal emanating from a read head positioned over the magnetic medium and generating a sequence of discrete time sample values;
(b) timing recovery for extracting timing information from the sequence of sample values;
(c) a discrete time sequence detector for detecting a bit sequence from the sequence of sample values;
(d) a sync mark detector, responsive to the sequence of discrete time sample values, for detecting the primary sync mark, wherein when the primary sync mark is undetectable due to errors, the sync mark detector detects the secondary sync mark;
(e) an input connected to receive the analog read signal;
(f) a frequency synthesizer for generating a periodic waveform;
(g) a multiplexor for multiplexing the analog read signal and the periodic waveform into the sampling device, wherein:
(i) the periodic waveform is selected as the input into the sampling device before reading a data sector in order to frequency lock timing recovery;
and
(ii) the analog read signal is selected as the input into the sampling device after frequency locking timing recovery in order to read an acquisition preamble and the data field;
and
(iii) when frequency lock is lost while reading the data field, then:
the periodic signal is selected as the input into the sampling device to re-establish frequency lock;
when frequency lock is re-established, the analog receive signal is again selected as the input to the sampling device in order to re-establish phase lock over the data field;
and
when phase lock is re-established, a secondary sync mark is detected to re-establish byte synchronization over the data field.

16 more elements

Dependencies are inferred from the claim text.

Thermal asperity compensation using multiple sync marks for retroactive and split segment data synchronization in a magnetic disk storage system

Life of this patent

Thermal asperity compensation using multiple sync marks for retroactive and split segment data synchronization in a magnetic disk storage system

Life of this patent

Abstract

Claims34