Speculative data streaming disk drive and system
View Patent ↗A disk drive capable of supporting speculative data transfers. Requested first data are read from the disk drive. Before the first data are read, a determination is made as to whether there are un-requested second data that are likely to be requested at a later time as part of a data stream. If so, then a determination is made as to whether the second data and the first data are stored in locations that are physically/logically proximate on the same disk. If the second data are close to the first data, then the second data are speculatively read and stored in a local disk cache. If a subsequent request comes to the disk drive for the second data, then the second data are quickly produced from the disk cache rather than being slowly read off the disk.
1. A secondary storage device capable of speculatively reading data, the secondary storage device comprising:
reading means for reading a first datum from a storage medium;
determining means for determining a probability of the secondary storage device receiving a read request for a second datum stored on the storage medium, the second datum being logically related to the first datum, and the determining means also, if the probability is above a pre-determined probability value, determining a cost to speculatively read the second datum, the cost being based on a position of a read/write head, relative to the second datum's physical location on the fixed medium, when the read/write head is reading the first datum;
storing means for, if the cost to speculatively read the second datum is below a pre-determined cost value, reading the second datum without a request being received from outside the secondary storage device for the second datum, the storing means then storing the second datum in a secondary storage device cache; and
producing means for producing the second datum from the secondary storage device cache if the secondary storage device receives a later request for the second datum.
2. The secondary storage device of claim 1 , wherein the secondary storage device comprises a hard disk drive.
3. The secondary storage device of claim 2 , wherein the storage medium is a magnetic disk.
4. The secondary storage device of claim 1 , wherein the storage medium is an optical disk.
5. The secondary storage device of claim 1 , wherein the probability of the secondary storage device receiving the request for the second datum is determined by a history of the second datum being requested when the first datum is requested.
6. The secondary storage device of claim 1 , wherein the probability of the secondary storage device receiving the request for the second datum is determined by a physical proximity of the first and second data on the storage medium.
7. The secondary storage device of claim 1 , wherein the cost to speculatively read the second data is determined by the first and second data being on a same track on the storage medium.
8. The secondary storage device of claim 1 , wherein the probability of the secondary storage device receiving the request for the second datum is determined by the first and second datum being of a same format.
9. The secondary storage device of claim 1 , wherein the first and second datum are on different disk surfaces associated with a first read/write head and a second read/write head respectively, and wherein the cost to speculatively read the second datum is determined by the second read/write head being near the physical location of the second datum when the first read/write head is near the physical location of the first datum.
10. A computer system comprising a secondary storage device capable of speculatively reading data, the computer system comprising:
a secondary storage device having reading means for reading a first datum from a storage medium;
determining means, in the secondary storage device, for determining a probability of the secondary storage device receiving a read request for a second datum stored on the storage medium, the second datum being logically related to the first datum, and the determining means also, if the probability is above a pre-determined probability value, determining a cost to speculatively read the second datum, the cost being based on a position of a read/write head, relative to the second datum's physical location on the fixed medium, when the read/write head is reading the first datum;
storing means in the secondary storage device for, if the cost to speculatively read the second datum is below a pre-determined cost value, reading the second datum without a request being received from outside the secondary storage device for the second datum, the storing means then storing the second datum in a secondary storage device cache; and
producing means in the secondary storage device for producing the second datum from the secondary storage device cache if the secondary storage device receives a later request for the second datum.
11. The computer system of claim 10 , wherein the secondary storage device comprises a hard disk drive.
12. The computer system of claim 11 , wherein the storage medium is a magnetic disk.
13. The computer system of claim 10 , wherein the storage medium is an optical disk.
14. The computer system of claim 10 , wherein the probability of the secondary storage device receiving the request for the second datum is determined by a history of the second datum being requested when the first datum is requested.
15. The computer system of claim 10 , wherein the probability of the secondary storage device receiving the request for the second datum is determined by a physical proximity of the first and second data on the storage medium.
16. The computer system of claim 10 , wherein the cost to speculatively read the second data is determined by the first and second data being on a same track on the storage medium.
17. The computer system of claim 10 , wherein the probability of the secondary storage device receiving the request for the second datum is determined by the first and second datum being of a same format.
18. The computer system of claim 10 , wherein the first and second datum are on different disk surfaces associated with a first read/write head and a second read/write head respectively, and wherein the cost to speculatively read the second datum is determined by the second read/write head being near the physical location of the second datum when the first read/write head is near the physical location of the first datum.