Detecting shingled overwrite errors

Patent metadata

Field	Value
Publication number	US-9536563-B1
Application number	US-201615044302-A
Country	US
Kind code	B1
Filing date	Feb 16, 2016
Priority date	Feb 16, 2016
Publication date	Jan 3, 2017
Grant date	Jan 3, 2017

Abstract

Systems and methods are disclosed for detecting shingled overwrite errors. When a read error is encountered when reading from shingled recording tracks, a processor may determine whether the read error is an error caused by shingled overwriting. The processor may determine whether the read error is caused by shingled overwriting by determining read signal quality of one or more sectors preceding the read error, such as based on a bit error count or bit error ratio (BER), and comparing the read signal quality to a threshold value. The processor may determine that the read error is caused by shingled overwriting when the read signal quality value is lower than the threshold.

First claim

What is claimed is:

1. An apparatus comprising:
a processor configured to:
detect a read error at a first sector when performing a read operation on shingled recording tracks;
determine whether the read error is an error caused by shingled overwriting; and
cancel error recovery operations for the first sector when the error is determined to be caused by shingled overwriting.

2. The apparatus of claim 1 comprising the processor further configured to:
determine whether the read error is caused by shingled overwriting by:
determining a read signal quality of one or more sectors preceding the first sector; and
determining whether the read error is caused by shingled overwriting based on comparing the read signal quality to a threshold value.

3. The apparatus of claim 2 comprising the processor further configured to:
determine the read signal quality based on a number of bit errors detected in the one or more sectors preceding the first sector; and
determine that the read error is caused by shingled overwriting when the read signal quality is less than the threshold value.

4. The apparatus of claim 3 comprising the processor further configured to:
calculate a bit error ratio (BER) based on the number of bit errors and a total number of bits read from the one or more sectors to determine the read signal quality; and
determine that the read error is caused by shingled overwriting when the BER is less than the threshold value.

5. The apparatus of claim 2 comprising the processor further configured to:
determine the read signal quality based on a variable gain amplifier (VGA) value for the one or more sectors preceding the first sector; and
determine that the read error is caused by shingled overwriting when the read signal quality is less than the threshold value.

6. The apparatus of claim 2 further comprising:
the one or more sectors include a plurality of sectors;
the processor further configured to:
determine an average read signal quality value by averaging read signal metrics for the plurality of sectors; and
determine whether the read error is caused by shingled overwriting based on comparing the average read signal quality value to the threshold value.

7. The apparatus of claim 6 further comprising:
a memory;
the processor further configured to:
allocate a buffer in the memory to store read signal metrics for the plurality of sectors; and
when the read error is encountered, access the buffer to determine the average read signal quality value.

8. The apparatus of claim 7 comprising the processor further configured to:
determine whether the buffer includes read signal metrics for a minimum number of sectors preceding the first sector; and
when the buffer does not include read signal metrics for the minimum number of sectors, perform an additional read operation on additional sectors preceding the first sector to reach the minimum number of sectors.

9. The apparatus of claim 1 comprising the processor further configured to:
when the error is determined to be caused by shingled overwriting, determine whether a data backup is available for data of the first sector; and
when the data backup is available, rewrite the first sector using the data backup.

10. The apparatus of claim 1 comprising the processor further configured to:
receive a read command from a host device directing the processor to perform the read operation;
perform error recovery operations on the first sector when the error is determined to not be caused by shingled overwriting; and
return a read error indicator to the host device when the error is determined to be caused by shingled overwriting.

11. A method comprising:
detecting a read error at a first sector when performing a read operation on shingled recording tracks of a data storage device;
determining whether the read error is an error caused by shingled overwriting of the first sector; and
canceling error recovery operations for the first sector when the error is determined to be caused by shingled overwriting.

12. The method of claim 11 further comprising:
determining whether the read error is caused by shingled overwriting by:
determining a read signal quality of one or more sectors preceding the first sector; and
determining whether the read error is caused by shingled overwriting based on comparing the read signal quality to a threshold value.

13. The method of claim 12 further comprising:
the one or more sectors include a plurality of sectors;
allocating a buffer in a memory to store read signal metrics for the plurality of sectors;
accessing the buffer to obtain the read signal metrics when the read error is encountered;
determining an average read signal quality value by averaging the read signal metrics; and
determining whether the read error is caused by shingled overwriting based on comparing the average read signal quality value to the threshold value.

14. The method of claim 13 further comprising:
determining whether the buffer includes read signal metrics for a minimum number of sectors preceding the first sector; and
when the buffer does not include read signal metrics for the minimum number of sectors, performing an additional read operation on additional sectors preceding the first sector to reach the minimum number of sectors.

15. The method of claim 11 further comprising:
determining whether a data backup is available for data of the first sector when the error is determined to be caused by shingled overwriting; and
rewriting the first sector using the data backup when the data backup is available.

16. The method of claim 11 further comprising:
receiving a read command from a host device at a data storage device to perform the read operation;
performing error recovery operations on the first sector when the error is determined to not be caused by shingled overwriting; and
returning a read error indicator from the data storage device to the host device when the error is determined to be caused by shingled overwriting.

17. A memory device storing instructions that, when executed, cause a processor to perform a method comprising:
detecting a read error at a first sector when performing a read operation on shingled recording tracks of a data storage device;
determining whether the read error is an error caused by shingled overwriting of the first sector; and
canceling error recovery operations for the first sector when the error is determined to be caused by shingled overwriting.

18. The memory device of claim 17 storing instructions that, when executed, cause the processor to perform a method further comprising:
determining whether the read error is caused by shingled overwriting by:
determining a read signal quality of one or more sectors preceding the first sector; and
determining whether the read error is caused by shingled overwriting based on comparing the read signal quality to a threshold value.

19. The memory device of claim 18 storing instructions that, when executed, cause the processor to perform a method further comprising:
the one or more sectors include a plurality of sectors;
allocating a buffer in a memory to store read signal metrics for the plurality of sectors;
accessing the buffer to obtain the read signal metrics when the read error is encountered;
determining an average read signal quality value by averaging the read signal metrics; and
determining whether the read error is caused by shingled overwriting based on comparing the average read signal quality value t

Assignees

• Seagate Technology Llc

Inventors

• Liu Xiong
• Zhou Weiqing
• Li Quan
• Xie Wenxiang

Classifications

• G11B2020/1292

  Enhancement of the total storage capacity · CPC title

• G11B20/1879 Primary

  Direct read-after-write methods · CPC title

• G11B2020/1238

  track, i.e. the entire a spirally or concentrically arranged path on which the recording marks are located · CPC title

• G11B20/1217

  on discs · CPC title

• G06F2212/462

  Track or segment · CPC title