Power efficient method for cold storage data retention management
A system and method for storing infrequently accessed data with reduced power consumption. In one embodiment, a solid state drive (SSD) includes flash memory and environmental data logging circuitry. The SSD is shut off or operated in a sleep mode to reduce power consumption, and turned on or transitioned to an active mode as needed when data on the SSD is to be accessed, or when a calculation, based on a number of erase cycles previously performed in the flash memory and on a temperature history of the SSD indicates that a data refresh may be needed to prevent data corruption in the SSD, due to data retention limitation of the nonvolatile memory in the SSD.
1. A method for operating a solid state drive (SSD) connected to a host, the SSD comprising nonvolatile memory and environmental data logging circuitry (EDLC) and a source of a battery power, the method comprising:
requesting, by the host, a length of a first time interval from the SSD;
providing, by the SSD, the length of the first time interval to the host;
discontinuing, by the host, during the first time interval, a primary power supplied to the SSD;
powering of the EDLC, by the SSD, from the source of the battery power during the first time interval;
logging, by the EDLC, of environmental data at a plurality of points in time;
restoring, by the host, of the primary power supplied to the SSD, at the end of the first time interval; and
refreshing of data stored in the SSD, by the SSD, when a module evaluated by the SSD indicates that, based on the logged environmental data, refreshing of the data is required.
2. The method of claim 1 , wherein the environmental data comprises a temperature of the SSD.
3. The method of claim 2 , wherein the environmental data comprises a time stamp.
4. The method of claim 1 , comprising recording, by the SSD, a number of erase cycles performed on the nonvolatile memory.
5. The method of claim 1 , wherein the providing, by the SSD, of the length of the first time interval to the host comprises executing a remaining data life module.
6. The method of claim 5 , wherein the remaining data life module is configured to accept as inputs a temperature history of the SSD since a most recent refresh, and a number of erase cycles previously performed on the nonvolatile memory.
7. A method for operating a solid state drive (SSD) connected to a host, the SSD comprising nonvolatile memory, the host comprising an environmental data logging system, the method comprising:
requesting, by the host, a length of a first time interval from the SSD;
providing, by the SSD, the length of the first time interval to the host;
discontinuing, by the host, during the first time interval, a power supplied to the SSD;
logging, by the environmental data logging system, of environmental data at a plurality of points in time during the first interval;
restoring, by the host, of the power supplied to the SSD, at the end of the first time interval;
providing, by the host, logged environmental data to the SSD; and
refreshing of data stored in the SSD, by the SSD, when a module evaluated by the SSD indicates that, based on the logged environmental data, refreshing of the data is required.
8. The method of claim 7 , wherein the environmental data comprises a temperature of the SSD.
9. The method of claim 8 , wherein the environmental data comprises a time stamp.
10. The method of claim 7 , comprising recording, by the SSD, a number of erase cycles performed on the nonvolatile memory.
11. The method of claim 7 , wherein the providing, by the SSD, the length of the first time interval to the host comprises executing a remaining data life module.
12. The method of claim 11 , wherein the remaining data life module is configured to accept as inputs a temperature history of the SSD since a most recent refresh, and a number of erase cycles previously performed on the nonvolatile memory.
13. A method for operating a solid state drive (SSD) connected to a host, the SSD comprising nonvolatile memory and environmental data logging circuitry (EDLC), the method comprising:
instructing, by the host, the SSD to transition to a sleep mode;
transitioning, by the SSD, to the sleep mode;
logging, by the EDLC, of environmental data at a plurality of points in time, while the SSD is in the sleep mode;
instructing, by the host, the SSD to transition to an active mode;
transitioning, by the SSD, to the active mode;
refreshing of data stored in the SSD, by the SSD, when a module evaluated by the SSD indicates that, based on the logged environmental data, refreshing of the data is required; and
sending, by the SSD, status information to the host, wherein the status information comprises a new sleep interval.
14. The method of claim 13 , wherein the environmental data comprises a temperature of the SSD.
15. The method of claim 14 , wherein the environmental data comprises a time stamp.
16. The method of claim 13 , comprising recording, by the SSD, a number of erase cycles performed on the nonvolatile memory.
17. The method of claim 13 , wherein the module evaluated by the SSD is configured to accept as inputs a temperature history of the SSD since a most recent refresh, and a number of erase cycles previously performed on the nonvolatile memory.