Data storage using identifiers
A system and method are disclosed for processing a data stream. A data segment is received. It is determined whether the data segment has been previously stored. In the event that the data segment is determined not to have been previously stored, a unique identifier for specifying the data segment in a representation of the data stream is generated.
1. A method for processing a data stream comprising:
receiving a data segment;
determining whether the data segment has been previously stored; and
in the event that the data segment is determined not to have been previously stored, generating a unique identifier for uniquely specifying the data segment in a representation of the data stream without probability of collision with a different data segment in the data stream; wherein
generating the unique identifier includes:
deriving a content derived summary based on content of the data segment;
determining whether a portion of the content derived summary has been previously stored; and
in the event that the portion of the content derived summary has not been previously stored, using the portion of the content derived summary as a unique identifier;
and wherein
the unique identifier is different from the content derived summary.
2. A method as recited in claim 1 , wherein no unique identifier for specifying the data segment in a representation of the data stream is generated in the event that the data segment is determined to have been previously stored.
3. A method as recited in claim 1 , wherein determining whether the data segment has been previously stored does not require using the unique identifier.
4. A method as recited in claim 1 , further comprising, in the event that the data segment is determined to have been previously stored, reusing a previously generated unique identifier associated with the data segment.
5. A method as recited in claim 1 , further comprising, in the event that the data segment is determined to have been previously stored, looking up a previously generated unique identifier associated with the data segment.
6. A method as recited in claim 1 , further comprising, in the event that the data segment is determined not to have been previously stored:
storing the data segment in a data segment storage location; and
recording the data segment storage location.
7. A method as recited in claim 6 , wherein the data segment storage location includes a memory address.
8. A method as recited in claim 1 , in the event that the data segment is determined not to have been previously stored, further including:
storing the data segment in a data segment storage location; and
updating a data structure for storing the content derived summary, the unique identifier, and the data segment storage location.
9. A method as recited in claim 1 in the event that the data segment is determined not to have been previously stored, further including:
storing the data segment in a data segment storage location; and
updating a data structure for storing the content derived summary, the unique identifier, and the data segment storage location; wherein
the data segment storage location is accessed given the unique identifier or given the content derived summary in the data structure.
10. A method as recited in claim 1 ,
in the event that the data segment is determined not to have been previously stored, further including:
storing the data segment in a data segment storage location; and
updating a data structure for storing the content derived summary, the unique identifier, and the data segment storage location; wherein
the data segment storage location is accessed given the unique identifier or given the content derived summary, using a single access of a storage device.
11. A method for processing a data stream as recited in claim 1 ,
in the event that the data segment is determined not to have been previously stored, further including:
storing the data segment in a data segment storage location; and
updating a data structure for storing the content derived summary, the unique identifier, and the data segment storage location; wherein
a region of the data structure that includes the data segment storage location is accessed given the unique identifier or given the content derived summary, using a single access of a storage device.
12. A method for processing a data stream as recited in claim 1 , wherein determining whether the data segment has been previously stored includes generating a content derived summary for the data segment; and the unique identifier is derived from the content derived summary.
13. A method as recited in claim 1 , in the event that the portion of the content derived summary has been previously stored, modifying a value that corresponds to the portion of the content derived summary to derive the unique identifier.
14. A system for processing data stream comprising:
an interface configured to receive a data segment;
a processor coupled to the interface, configured to:
determine whether the data segment has been previously stored; and
in the event that the data segment is determined not to have been previously stored, generate a unique identifier for uniquely specifying the data segment in a representation of the data stream without probability of collision with a different data segment in the data stream; wherein
generating the unique identifier includes:
deriving a content derived summary based on content of the data segment;
determining whether a portion of the content derived summary has been previously stored;
in the event that the portion of the content derived summary has not been previously stored, using the portion of the content derived summary as a unique identifier;
wherein
the unique identifier is different from the content derived summary.
15. A system as recited in claim 14 , wherein no unique identifier for specifying the data segment in a representation of the data stream is generated in the event that the data segment is determined to have been previously stored.
16. A system as recited in claim 14 , wherein determining whether the data segment has been previously stored does not require using the unique identifier.
17. A system as recited in claim 14 , the processor is further configured, in the event that the portion of the content derived summary has been previously stored, to modify a value that corresponds to the portion of the content derived summary to derive the unique identifier.
18. A computer program product for processing a data stream, the computer program product being embodied in a computer readable storage medium and comprising computer instructions for:
receiving a data segment;
determining whether the data segment has been previously stored; and
in the event that the data segment is determined not to have been previously stored, generating a unique identifier uniquely specifying the data segment in a representation of the data stream without probability of collision with a different data segment in the data stream; wherein
generating the unique identifier includes:
deriving a content derived summary based on content of the data segment;
determining whether a portion of the content derived summary has been previously stored; and
in the event that the portion of the content derived summary has not been previously stored, using the portion of the content derived summary as a unique identifier;
and wherein
the unique identifier is different from the content derived summary.
19. A computer program product as recited in claim 18 , wherein no unique identifier for specifying the data segment in a representation of the data stream is generated in the event that the data segment is determined to have been previously stored.
20. A computer program product as recited in claim 18 , wherein determining whether the data segment has been previously stored does not require using the unique identifier.
21. A computer program product as recited in claim 18 , further comprising computer instructions for in the event that the portion of the content derived summary has been previously stored, modifying a value that corresponds to the portion of the content derived summary to derive the unique identifier.