Power conservation based on caching
View Patent ↗The present invention relates to a method and device that conserves power. In some embodiments, the device is a battery powered storage device. The invention employs a large cache and aggressive caching algorithm to serve data from the storage media (hard disk or SSD) or write data to the storage media. The cache provides an efficient location from which to serve data, especially multi-media. In one embodiment, the algorithm determines when to place the drive into a lower power state, such as idle, or standby, based on the amount of anticipated idle time provided by the large cache.
1. A method of conserving power in a storage device comprising a wireless interface, a storage medium, a memory, and a bulk cache, said method comprising:
receiving a request for a file stored on the storage medium;
determining whether a block size associated with the file is greater than a threshold;
when the block size is less than the threshold, servicing the file from the memory; and
when the block size is greater than the threshold:
caching the file in the bulk cache;
servicing the file from the bulk cache;
determining a time period that the bulk cache can service the request based at least in part on a difference between fill rate and drain rate associated with the bulk cache and a transmission rate of the wireless interface; and
placing the storage device in a low power state for the time period.
2. The method of claim 1 , wherein the wireless interface comprises a WiFi wireless interface.
3. The method of claim 1 , wherein the storage device is a hard-disk drive.
4. The method of claim 1 , wherein the block size is 256 MB.
5. The method of claim 1 , wherein said receiving the request for the file comprises receiving a request for streaming a multimedia file over the wireless interface.
6. The method of claim 1 , wherein determining whether the block size is greater than the threshold is based on the size of the file and whether the file is to be streamed over the wireless interface.
7. The method of claim 1 , wherein said placing the storage device in the low power state is based on a number of simultaneous users requesting files from the storage device.
8. The method of claim 1 , wherein said placing the storage device in the low power state comprises placing the storage device in a standby state.
9. The method of claim 8 , wherein the standby state is an active standby state.
10. The method of claim 8 , wherein the standby state is a low standby state.
11. The method of claim 1 , wherein said placing the storage device in the low power state comprises placing the storage device in a sleep state.
12. A storage device comprising:
a wireless interface configured to provide a wireless connection to at least one client;
a memory;
a bulk cache;
a storage medium; and
a controller configured to:
receive a host request for a file stored on the storage medium;
determine whether a block size associated with the file is greater than a threshold;
when the block size is determined to be less than the threshold, service the file from the memory; and
when the block size is determined to be greater than the threshold;
service the file from the bulk cache;
determine a time period based at least in part on a difference between fill rate and drain rate associated with the bulk cache and a transmission rate of the wireless interface; and
place the storage device in a low power state for the time period.
13. The storage device of claim 12 , wherein the bulk cache comprises at least 2 GB of memory.
14. The storage device of claim 12 , wherein the controller is further configured to reduce power consumption for operating the storage medium in the low power state.
15. The storage device of claim 12 , wherein the controller is further configured to prefetch blocks of at least 256 MB in the bulk cache for multimedia files streamed via the wireless interface.
16. The storage device of claim 12 , wherein the controller is further configured to:
determine a set of additional files related to the requested file; and
prefetch the additional files into the bulk cache.
17. The storage device of claim 12 , wherein the controller is further configured to determine a time to next access of the storage medium based on a data rate of the wireless interface and rate of consumption by the at least one client.
18. The storage device of claim 17 , wherein the controller is further configured to place the storage medium in a standby state based on the time to next access.
19. The storage device of claim 17 , wherein the controller is further configured to place the storage medium in an idle state based on the time to next access.
20. The storage device of claim 17 , wherein the controller is further configured to place the storage medium in an active state based on the time to next access and a time required to spin up the storage medium.