Accessing data in a content-addressable data processing system

Abstract

A computer-implemented method operable in a computer system comprising a plurality of computers including at least a first computer and at least two second computers, the method includes: obtaining a first identifier from the first computer at the at least two second computers, said first identifier having been determined, at least in part, by applying a first function to the content of the data item, wherein the first function comprises a hash function; and at least one of the at least two second computers using the first identifier to ascertain a storage location for the data item on the computer system. At least one of the at least two second computers may use the first identifier to access the data item on the computer system. The method may include verifying that the content of the data item has not changed since creation of the first identifier.

1 . A computer-implemented method operable in a computer system comprising a plurality of computers including at least a first computer and at least two second computers, the method comprising:
 (A) obtaining a first identifier from the first computer at the at least two second computers, said first identifier having been determined, at least in part, by applying a first function to the content of the data item, wherein the first function comprises a hash function; and   (B) at least one of the at least two second computers using the first identifier to ascertain a storage location for the data item on the computer system.   
     
     
         2 . The method of  claim 1  further comprising:
 at least one of the at least two second computers using the first identifier to access the data item on the computer system. 
 
     
     
         3 . The method of  claim 1  further comprising:
 (C) verifying that the content of the data item has not changed since creation of the first identifier. 
 
     
     
         4 . The method of  claim 1 , further comprising:
 creating the first identifier based on the entire content of the data item.   
     
     
         5 . The method of  claim 1 , wherein a data item may comprise a file, a portion of a file, a page in memory, a digital message, a portion of a digital message, a digital image, a portion of a digital image, a video signal, a portion of a video signal, an audio signal, or a portion of an audio signal, a software product, or a portion of a software product, or a sequence of identifiers for components of a compound data item. 
     
     
         6 . The method of  claim 1 , wherein the first identifier is obtained in (A) with a request from the first computer. 
     
     
         7 . The method of  claim 6  wherein the first identifier is the only identifier the first computer uses to identify the data item in the request. 
     
     
         8 . The method of  claim 1  wherein the hash function is selected from the functions: MD4, MD5, and SHA. 
     
     
         9 . The method of  claim 1 , wherein the hash function comprises a cryptographic hash function, and wherein the first identifier was determined by applying the cryptographic hash function to the entire content of the data item. 
     
     
         10 . The method of  claim 1 , wherein the data item includes a second identifier for at least one digital data item, and wherein the second identifier for the at least one digital data item is based, at least in part, on the content of the digital data item. 
     
     
         11 . The method of  claim 1 , wherein the computer system comprises a plurality of computers in addition to the first computer and the at least two second computers, wherein the plurality of computers are interconnected by at least one network, and wherein each of the plurality of computers manages storage of one or more data items. 
     
     
         12 . The method of  claim 1 , wherein the first computer and the at least two second computers are peer computers coupled by at least one network. 
     
     
         13 . The method of  claim 1 , wherein storage of the data item is managed by at least one of the at least two second computers. 
     
     
         14 . The method of  claim 1 , wherein the data item is stored on the at least one of the at least two second computers. 
     
     
         15 . The method of  claim 1 , wherein the data item is stored by the at least one of the at least two second computers on a storage device managed by the at least one of the at least two second computers. 
     
     
         16 . The method of  claim 6 , wherein the request comprises request to read the data item. 
     
     
         17 . The method of  claim 16 , wherein the first computer issued the request to read the data item, and wherein the method further comprises act of:
 transmitting the data item from the at least one of the second computers to the first computer.   
     
     
         18 . The method of  claim 16 , wherein the first computer issued the request, and wherein the method further comprises:
 transmitting the data item to the first computer from a computer distinct from the at least one of the second computers.   
     
     
         19 . The method of  claim 6 , wherein the request comprises request to delete the data item, and wherein the method further comprises:
 deleting the data item in response to the request.   
     
     
         20 . The method of  claim 3 , wherein act (C) of verifying comprises:
 (D) generating a second identifier for the data item based upon the content of the data item; and   (E) comparing the second identifier to the first identifier to verify that the first identifier and the second identifier are identical.   
     
     
         21 . The method of  claim 20 , wherein the hash function comprises a cryptographic hash function, and wherein the act (D) comprises generating the second identifier by applying the cryptographic hash function to the at least a portion of the content of the data item. 
     
     
         22 . The method of  claim 20 , wherein the hash function comprises a cryptographic hash function, and wherein the act (A) comprises generating the first identifier by applying the cryptographic hash function to the entire content of the data item, and wherein the act (D) comprises generating the second identifier by applying the cryptographic hash function to the entire content of the data item. 
     
     
         23 . The method of  claim 1 , wherein the at least one of the at least two second computers comprises a file system to manage data items stored by the at least one of the at least two second computers, wherein the first identifier is used as a name of a file in which the data item is stored by the at least one of the at least two second computers, and wherein the method further comprises:
 using the first identifier to index into the file system to locate the data item.   
     
     
         24 . The method of  claim 1  further comprising:
 obtaining the first identifier at the first computer. 
 
     
     
         25 . The method of  claim 1 , wherein at least one of the at least two second computers comprises a file server. 
     
     
         26 . The method of  claim 1 , wherein at least one of the at least two second computers comprises a storage system. 
     
     
         27 . The method of  claim 3 , wherein storage of the data item is managed by the at least one of the at least two second computers, wherein the act (C) is performed by the first computer. 
     
     
         28 . The method of  claim 6 , wherein the request comprises request to have the data item stored by the at least one of the at least two second computers. 
     
     
         29 . The method of  claim 28 , further comprising acts, performed by the at least one of the at least two second computers in response to receipt of the request, of:
 storing the data item in at least one storage location managed by the at least one of the at least two second computers; and   associating the storage location with the first identifier.   
     
     
         30 . The method of  claim 1 , further comprising:
 receiving the first identifier at the at least one of the at least two second computers.   
     
     
         31 . The method of  claim 6 , further comprising an act, performed by the at least one of the at least two second computers in response to receipt of the request, of generating the first identifier. 
     
     
         32 . The method of  claim 1 , wherein first identifier for a data item is based, at least in part, on a size or length of the data item. 
     
     
         33 . The method of  claim 6 , wherein the request comprises the first identifier, and wherein the method further comprises acts of:
 receiving the data item at the first computer;   generating, at the first computer, a second identifier for the data item received at the first computer; and   comparing the second identifier to the first identifier to verify that the first identifier and the second identifier are identical.   
     
     
         34 . The method of  claim 6 , wherein the first computer issued the request, and wherein the method further comprises:
 receiving the data item at the first computer.   
     
     
         35 . The method of  claim 1 , further comprising:
 associating, at the first computer, the data item with the first identifier.   
     
     
         36 . A computer-implemented method operable in a computer system comprising a plurality of computers including at least a first computer and at least two second computers, the method comprising:
 (A) obtaining a first identifier from the first computer at the at least two second computers, said first identifier having been determined, at least in part, by applying a first function to the entire content of the data item, said first function comprising a cryptographic hash function, said first identifier being part of a request from the first computer, wherein the first identifier is the only identifier the first computer uses to identify the data item in the request;   (B) at least one of the at least two second computers using the first identifier to try locate a storage location for the data item on the computer system;   (C) at least one of the at least two second computers using the first identifier to access the data item on the computer system; and   (D) verifying that the content of the data item has not changed since creation of the first identifier.   
     
     
         37 . A computer-implemented method operable in a computer system comprising a plurality of computers including at least a first computer and at least two second computers, wherein the at least one of the at least two second computers comprises a file system to manage data items stored by the at least one of the at least two second computers, wherein the first identifier is used as a name of a file in which the data item is stored by the at least one of the at least two second computers, the method comprising:
 (A) obtaining a first identifier from the first computer at the at least two second computers, said first identifier having been determined, at least in part, by applying a first function to the entire content of the data item, said first function comprising a cryptographic hash function, said first identifier being part of a request from the first computer, wherein the first identifier is the only identifier the first computer uses to identify the data item in the request;   (B) at least one of the at least two second computers using the first identifier to try locate a storage location for the data item on the computer system using the first identifier to index into the file system to locate the data item; and   (C) at least one of the at least two second computers using the first identifier to access the data item on the computer system.