Detecting shingled overwrite errors

• US 9,536,563 B1
• Filed: 02/16/2016
• Issued: 01/03/2017
• Est. Priority Date: 02/16/2016
• Status: Active Grant

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Seagate Technology LLC (Seagate Technology Holdings Plc)
• Inventors: Zhou, WeiQing, Liu, Xiong, Li, Quan, Xie, WenXiang
• Primary Examiner(s): Agustin, Peter Vincent
• Application Number:
  US15/044,302
• Time in Patent Office: 322 Days
• Field of Search: None
• US Class Current: 1/1
• CPC Class Codes: G06F 11/0727 in a storage system, e.g. in a DASD or network based storage system drivers for digital recording or reproducing units G06F3/06; circuits for error detection or correction within digital recording or reproducing units G11B20/18; for distributed storage of data in networks, e.g. transport arrangements for network file system [NFS], storage area networks [SAN] or network attached storage [NAS], H04L67/1097
• CPC Class Codes: G06F 11/076 by exceeding a count or rate limit, e.g. word- or bit count limit
• CPC Class Codes: G06F 11/079 Root cause analysis, i.e. error or fault diagnosis in a hardware test environment G06F11/22; in a software test environment G06F11/36
• CPC Class Codes: G06F 11/0793 Remedial or corrective actions recovery from an exception in an instruction pipeline G06F9/3861; by retry G06F11/1402; for recovering from a failure of a protocol instance or entity H04L69/40
• CPC Class Codes: G06F 11/1469 Backup restoration techniques
• CPC Class Codes: G06F 12/0871 Allocation or management of cache space
• CPC Class Codes: G06F 2201/81 Threshold
• CPC Class Codes: G06F 2212/1032 Reliability improvement, data loss prevention, degraded operation etc
• CPC Class Codes: G06F 2212/281 Single cache
• CPC Class Codes: G06F 2212/462 Track or segment
• CPC Class Codes: G11B 20/10009 Improvement or modification of read or write signals
• CPC Class Codes: G11B 20/1217 on discs
• CPC Class Codes: G11B 20/1879 Direct read-after-write methods
• CPC Class Codes: G11B 2020/1238 track, i.e. the entire a spirally or concentrically arranged path on which the recording marks are located
• CPC Class Codes: G11B 2020/1292 Enhancement of the total storage capacity

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.

Claims

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 to the threshold value.

20. The memory device of claim 17 storing instructions that, when executed, cause the processor to perform a method 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.