Defective memory unit screening in a memory system

1. A memory system, comprising:

non-volatile media having a set of memory units;

a controller configured to process requests from a host system to store data in the non-volatile media or retrieve data from the non-volatile media;

wherein the memory system stores an indicator indicating whether the memory system is operating in a user mode or a manufacturing mode; and

wherein a defect manager of the memory system identifies a threshold based on the indicator, monitors an error rate in reading data from the non-volatile media and, in response to the error rate reaching the threshold, screens the non-volatile media for defective memory units.

2. The memory system of claim 1 , wherein the non-volatile media includes a flash memory.

3. The memory system of claim 2 , wherein the memory system is a solid-state drive.

4. The memory system of claim 3 , wherein the threshold is lower when the memory system is operating in the manufacturing mode than when the memory system is operating in the user mode.

5. The memory system of claim 4 , wherein when the memory system is operating in the manufacturing mode the controller is configured to perform at least one function that is not performed in the user mode.

6. The memory system of claim 5 , wherein the function relates to testing or diagnosis in a manufacturing facility.

7. The memory system of claim 5 , wherein after completion of manufacturing of the memory system, the indicator is adjusted to indicate that the memory system is operating in the user mode.

8. The memory system of claim 5 , wherein during screening of the non-volatile media for defective memory units, the defect manager identifies memory units that have errors in retrieved data after retrying reading for more than a threshold number of times.

9. The memory system of claim 5 , wherein during screening of the non-volatile media for defective memory units, the defect manager identifies memory units that fail to store data correctly.

10. The memory system of claim 5 , wherein the defect manager identifies a priority for screening defective memory units based on an error log.

11. The memory system of claim 5 , wherein the indicator is set by the host system during a power-on startup operation.

12. A method, comprising:

processing, by a controller of a memory system having non-volatile media, requests from a host system to store data in the non-volatile media or retrieve data from the non-volatile media, the non-volatile media having a set of memory units;

storing, in the memory system, an indicator indicating whether the memory system is operating in a user mode or a manufacturing mode;

identifying, by a defect manager of the memory system, a threshold based on the indicator;

monitoring, by the defect manager, an error rate in reading data from the non-volatile media; and

in response to the error rate reaching the threshold, screening by the defect manager the non-volatile media for defective memory units.

13. The method of claim 12 , wherein the non-volatile media includes a flash memory; the memory system is a solid-state drive; and the host system and the memory system communicate over a communication channel in accordance with a communication protocol for peripheral component interconnect express bus.

14. The method of claim 13 , wherein:

in response to the memory system operating in the manufacturing mode, a manufacturing mode threshold is identified; and

the screening of the non-volatile media for defective memory units is in response to the error rate reaching the manufacturing mode threshold;

in response to the memory system operating in the user mode, a user mode threshold is identified; and

the screening of the non-volatile media for defective memory units is in response to the error rate reaching the user mode threshold; and

the manufacturing mode threshold is lower than the user mode threshold.

15. The method of claim 14 , further comprising:

in response to the memory system operating in the manufacturing mode, performing by the controller at least one testing or diagnosis function that is not performed in the user mode.

16. The method of claim 15 , wherein the screening of the non-volatile media for defective memory units includes identifying memory units that have errors in retrieved data after retrying reading for more than a threshold number of times.

17. The method of claim 16 , wherein the screening of the non-volatile media for defective memory units includes identifying memory units that fail to store data.

18. The method of claim 17 , further comprising:

identifying a priority for screening defective memory units based on a log of errors recorded in reading data from memory units where errors are removed via at least one of:

retry of read operations; and

error correction made using redundant information.

19. A non-transitory computer storage medium storing instructions which, when executed by a memory system having non-volatile media, and a controller, cause the memory system to perform a method, the method comprising:

processing, by the controller, requests from a host system to store data in the non-volatile media or retrieve data from the non-volatile media, the non-volatile media having a set of memory units;

identifying a threshold based on whether the memory system is operating in a user mode or a manufacturing mode;

monitoring an error rate in reading data from the non-volatile media; and

in response to the error rate reaching the threshold, screening the non-volatile media for defective memory units.

20. The non-transitory computer storage medium of claim 19 , wherein:

when the memory system is operating in the manufacturing mode, a manufacturing mode threshold is identified; and

the screening of the non-volatile media for defective memory units is in response to the error rate reaching the manufacturing mode threshold;

when the memory system is operating in the user mode, a user mode threshold is identified; and

the screening of the non-volatile media for defective memory units is in response to the error rate reaching the user mode threshold; and

the manufacturing mode threshold is lower than the user mode threshold.