System and method for managing off-track read retry
The technology disclosed herein pertains to a system and method for managing off-track retry. An implementation of a method of determining offset direction for read off-track retry includes storing analog to digital converter (ADC) values of data read from a data sector by a data reader in a read channel buffer, calculating an indicator value of the distribution of the ADC values, determining an amount of offset for the data reader based on the indicator value, and moving the data reader by the amount of offset before performing a read retry operation.
1. A method of determining offset direction for read off-track retry, the method comprising:
storing analog to digital converter (ADC) values of data read from a data sector by a data reader in a read channel buffer;
calculating an indicator value of the distribution of the ADC values;
determining an amount of offset for the data reader based on the indicator value; and
moving the data reader by the amount of offset before performing a read retry operation.
2. The method of claim 1 , wherein determining the indicator value further comprising:
calculating a first cumulative distribution function (CDF) value of data values at a lower ADC value;
calculating a second CDF value of data values at a predetermined mid ADC value;
determining a first delta between the first CDF value and the second CDF value as the indicator value.
3. The method of claim 2 , wherein the ADC values are generated by a six-bit ADC and the lower ADC value is −32 bit.
4. The method of claim 3 , wherein the mid ADC value is −22.
5. The method of claim 2 , further comprising:
offsetting the data reader by a predetermined percentage track pitch (TP) to left;
determining a second delta between the first CDF value and the second CDF value; and
in response to determining that the first delta is less than the second delta:
substituting the second delta for the first delta, and
further offsetting the data reader by the predetermined percentage track pitch (TP) to left.
6. The method of claim 5 , further comprising:
in response to determining that the first delta is greater than the second delta:
substituting the second delta for the first delta, and
further offsetting the data reader by the predetermined percentage TP to right.
7. The method of claim 5 , wherein the first predetermined percentage TP is substantially four (4) percent.
8. The method of claim 5 , further comprising:
in response to determining that the first delta is substantially similar to the second delta reducing the value of the predetermined percentage TP.
9. A storage device, comprising:
a data reader to read data to various sectors of the storage device;
an analog to digital converter (ADC) to convert the read data into digital values; and
an off-track read retry manager configured to store one or more computer readable instructions for executing on a computer system a computer process, the computer process comprising:
storing analog to digital converter (ADC) values of data read from a data sector by a data reader in a read channel buffer;
calculating an indicator value of the distribution of the ADC values;
determining an amount of offset for the data reader based on the indicator value; and
moving the data reader by the amount of offset before performing a read retry operation.
10. The storage device of claim 9 , wherein determining the indicator value further comprising:
calculating a first cumulative distribution function (CDF) value of data values at a lower ADC value;
calculating a second CDF value of data values at a predetermined mid ADC value;
determining a first delta between the first CDF value and the second CDF value as the indicator value.
11. The storage device of claim 10 , wherein the ADC values are generated by a six-bit ADC and the lower ADC value is −32 bit and wherein the mid ADC value is −22.
12. The storage device of claim 11 , further comprising:
offsetting the data reader by a predetermined percentage track pitch (TP) to left;
determining a second delta between the first CDF value and the second CDF value; and
in response to determining that the first delta is less than the second delta:
substituting the second delta for the first delta, and
further offsetting the data reader by the predetermined percentage track pitch (TP) to left.
13. The storage device of claim 12 , further comprising:
in response to determining that the first delta is greater than the second delta:
substituting the second delta for the first delta, and
further offsetting the data reader by the predetermined percentage TP to right.
14. The storage device of claim 12 , wherein the first predetermined percentage TP is substantially four (4) percent.
15. The storage device of claim 12 , further comprising:
in response to determining that the first delta is substantially similar to the second delta reducing the value of the predetermined percentage TP.
16. One or more processor-readable non-transitory storage media encoding processor-executable instructions for executing on a computer system a computer process, the computer process comprising:
storing analog to digital converter (ADC) values of data read from a data sector by a data reader in a read channel buffer;
calculating an indicator value of the distribution of the ADC values;
determining an amount of offset for the data reader based on the indicator value; and
moving the data reader by the amount of offset before performing a read retry operation.
17. The one or more processor-readable non-transitory storage media of claim 16 , wherein determining the indicator value further comprising:
calculating a first cumulative distribution function (CDF) value of data values at a lower ADC value;
calculating a second CDF value of data values at a predetermined mid ADC value;
determining a first delta between the first CDF value and the second CDF value as the indicator value.
18. The one or more processor-readable non-transitory storage media of claim 17 , wherein the ADC values are generated by a six-bit ADC and the lower ADC value is −32 bit and wherein the mid ADC value is −22.
19. The one or more processor-readable non-transitory storage media of claim 18 , wherein the computer process further comprising:
offsetting the data reader by a predetermined percentage track pitch (TP) to left;
determining a second delta between the first CDF value and the second CDF value; and
in response to determining that the first delta is less than the second delta:
substituting the second delta for the first delta, and
further offsetting the data reader by the predetermined percentage track pitch (TP) to left.
20. The one or more processor-readable non-transitory storage media of claim 19 , wherein the computer process further comprising:
in response to determining that the first delta is greater than the second delta:
substituting the second delta for the first delta, and
further offsetting the data reader by the predetermined percentage TP to right.