Non-volatile semiconductor storage device
According to one embodiment, there is provided a non-volatile semiconductor storage device including a non-volatile memory, a monitoring section, a determining section, and a notification processing section. The non-volatile memory includes a plurality of memory cells driven by word lines and a voltage generating section that generates a read voltage to be applied to the word lines. The monitoring section monitors a change in a threshold distribution of the plurality of memory cells upon performing a read processing to read data from the plurality of memory cells by applying the read voltage to the word lines. The determining section determines a degree of deterioration of the non-volatile memory in accordance with a monitoring result by the monitoring section. The notification processing section notifies a life of the non-volatile memory in accordance with a determining result by the determining section.
1. A storage system comprising:
a non-volatile memory including a plurality of memory cells; and
a controller configured to perform at least one of a first operation, a second operation, a third operation, and a fourth operation,
the first operation including
monitoring a number of reading operations in a read processing until the read processing succeeds, while repeatedly performing the read processing by gradually changing a read voltage in one of an increasing direction and a lowering direction, and
determining a degree of deterioration of the non-volatile memory in accordance with a result of the monitoring;
the second operation including
monitoring an amount of change of a read voltage from a default value in a read processing when the read processing succeeds, while repeatedly performing the read processing by gradually changing the read voltage in one of an increasing direction and a lowering direction, and
determining a degree of deterioration of the non-volatile memory in accordance with a result of the monitoring;
the third operation including
monitoring a number of bit errors in data in the plurality of memory cells in performing a read processing, and
determining a degree of deterioration of the non-volatile memory in accordance with a result of the monitoring;
the fourth operation including
monitoring a number of reading operations in a read processing until the read processing succeeds or an amount of change of a read voltage from a default value in a read processing when the read processing succeeds, while repeatedly performing the read processing by gradually changing the read voltage in both of an increasing direction and a lowering direction, and
determining a degree of deterioration of the non-volatile memory in accordance with a result of the monitoring.
2. The storage system according to claim 1 ,
wherein the first operation includes
comparing the monitored number of reading operations in the read processing with a predetermined threshold, and
determining the degree of deterioration of the non-volatile memory in accordance with a comparison result thereof.
3. The storage system according to claim 1 ,
wherein the second operation includes
comparing the monitored amount of change of the read voltage with a predetermined threshold, and
determining the degree of deterioration of the non-volatile memory in accordance with a comparison result thereof.
4. The storage system according to claim 1 ,
wherein the third operation includes
comparing the monitored number of bit errors with a predetermined threshold, and
determining the degree of deterioration of the non-volatile memory in accordance with a comparison result thereof.
5. The storage system according to claim 1 ,
wherein the fourth operation includes
comparing, with a predetermined threshold, the monitored number of reading operations in the read processing or the monitored amount of change of the read voltage, and
determining the degree of deterioration of the non-volatile memory in accordance with a comparison result thereof.
6. The storage system according to claim 1 ,
wherein the storage system is connectable to a host apparatus including a display device, and
the controller is further configured to notify, via the display device, a life of the non-volatile memory based on the determined degree of deterioration of the non-volatile memory.
7. A method of controlling a non-volatile memory including a plurality of memory cells, the method comprising:
performing at least one of a first operation, a second operation, a third operation, and a fourth operation,
the first operation including
monitoring a number of reading operations in a read processing until the read processing succeeds, while repeatedly performing the read processing by gradually changing a read voltage in one of an increasing direction and a lowering direction, and
determining a degree of deterioration of the non-volatile memory in accordance with a result of the monitoring;
the second operation including
monitoring an amount of change of a read voltage from a default value in a read processing when the read processing succeeds, while repeatedly performing the read processing by gradually changing the read voltage in one of an increasing direction and a lowering direction, and
determining a degree of deterioration of the non-volatile memory in accordance with a result of the monitoring;
the third operation including
monitoring a number of bit errors in data in the plurality of memory cells in performing a read processing, and
determining a degree of deterioration of the non-volatile memory in accordance with a result of the monitoring;
the fourth operation including
monitoring a number of reading operations in a read processing until the read processing succeeds or an amount of change of a read voltage from a default value in a read processing when the read processing succeeds, while repeatedly performing the read processing by gradually changing the read voltage in both of an increasing direction and a lowering direction, and
determining a degree of deterioration of the non-volatile memory in accordance with a result of the monitoring.
8. The method according to claim 7 ,
wherein the first operation includes
comparing the monitored number of reading operations in the read processing with a predetermined threshold, and
determining the degree of deterioration of the non-volatile memory in accordance with a comparison result thereof.
9. The method according to claim 7 ,
wherein the second operation includes
comparing the monitored amount of change of the read voltage with a predetermined threshold, and
determining the degree of deterioration of the non-volatile memory in accordance with a comparison result thereof.
10. The method according to claim 7 ,
wherein the third operation includes
comparing the monitored number of bit errors with a predetermined threshold, and
determining the degree of deterioration of the non-volatile memory in accordance with a comparison result thereof.
11. The method according to claim 7 ,
wherein the fourth operation includes
comparing, with a predetermined threshold, the monitored number of reading operations in the read processing or the monitored amount of change of the read voltage, and
determining the degree of deterioration of the non-volatile memory in accordance with a comparison result thereof.
12. The method according to claim 7 , further comprising:
connecting to a host apparatus including a display device, and
notifying, via the display device, a life of the non-volatile memory based on the determined degree of deterioration of the non-volatile memory.
13. A storage system comprising:
a non-volatile memory including a plurality of memory cells; and
a controller configured to perform a read processing to read data from the plurality of memory cells, to obtain a distribution of read-related parameters which indirectly indicates a change in a threshold distribution, and to determine a degree of deterioration of the non-volatile memory based on the obtained distribution,
wherein the controller compares the obtained distribution with a first threshold to determine the degree of deterioration of the non-volatile memory, and further compares a comparison result with a second threshold to determine the degree of deterioration of the non-volatile memory.
14. The storage system according to claim 13 ,
wherein the obtained distribution of the read-related parameters includes a distribution of the reading numbers of the plurality of memory cells, and
the first threshold includes a number threshold.
15. The storage system according to claim 14 ,
wherein the comparison result includes a frequency of the reading numbers that is at or more than the number threshold, and
the second threshold includes a frequency threshold.
16. The storage system according to claim 13 ,
wherein the obtained distribution of the read-related parameters includes a distribution of changing amounts of the read voltage of the plurality of memory cells, and
the first threshold includes a changing amount threshold.
17. The storage system according to claim 16 ,
wherein the comparison result includes a frequency of the changing amounts of the read voltage that is at or more than the changing amount threshold, and
the second threshold includes a frequency threshold.
18. The storage system according to claim 13 ,
wherein the obtained distribution of the read-related parameters includes a distribution of bit error numbers of the plurality of memory cells, and
the first threshold includes a bit error number threshold.
19. The storage system according to claim 18 ,
wherein the comparison result includes a frequency of the bit error numbers that is at or more than the bit error number threshold, and
the second threshold includes a frequency threshold.
20. The storage system according to claim 13 ,
wherein the storage system is connectable to a host apparatus including a display device, and
the controller notifies, via the display device, the obtained distribution of the read-related parameters, the first threshold, the comparison result, and the second threshold.