Intelligent slice caching

Abstract

Systems and methods for intelligent slice caching in a dispersed storage network. The methods include determining a minimum slice access rate for encoded data slices to be stored, determining a least access rate of a least accessed encoded data slice stored, determining an estimated access rate for an encoded data slice and determining whether to store the encoded data slice in small fast memory as a cached encoded data slice based on the minimum slice access rate, the least access rate, and the estimated access rate. The method further includes facilitating storage of the encoded data slice in small fast memory. The method may also include updating the minimum slice access rate and transferring an encoded data slice stored in small fast memory to large slow memory when an actual access rate is less than the minimum slice access rate or is less than the least access rate.

What is claimed is: 
     
         1 . A method of storing data in a dispersed storage network, the dispersed storage network including a plurality of dispersed storage units, the method comprising:
 determining a minimum slice access rate for storing slices in a first memory of a first dispersed storage unit of the plurality of dispersed storage units;   determining a least access rate of a least accessed encoded data slice stored in the first memory of the first dispersed storage unit of the plurality of dispersed storage units;   determining an estimated access rate for an encoded data slice to be stored;   determining whether to store the encoded data slice to be stored in the first memory of the first dispersed storage unit of the plurality of dispersed storage units based on the minimum slice access rate for storing slices in the first memory of the first dispersed storage unit of the plurality of dispersed storage units, the least access rate of the least accessed encoded data slice stored in the first memory of the first dispersed storage unit of the plurality of dispersed storage units and the estimated access rate for the encoded data slice to be stored to produce a determination; and   storing the encoded data slice to be stored in the first memory based on the determination.   
     
     
         2 . The method of  claim 1 , wherein first memory includes a small fast memory and wherein the first dispersed storage unit of the plurality of dispersed storage units further includes a second memory, the second memory including a large slow memory. 
     
     
         3 . The method of  claim 2  wherein the step of storing the encoded data slice to be stored in the first memory based on the determination includes transferring the encoded data slice from the second memory to the first memory. 
     
     
         4 . The method of  claim 1 , wherein the step of determining the minimum slice access rate for storing slices in the first memory of the first dispersed storage unit of the plurality of dispersed storage units is based on one or more of a historical access rate, a memory wear factor and a capacity level of the first memory. 
     
     
         5 . The method of  claim 4 , wherein the memory wear factor includes a maximum number of writes per unit of time. 
     
     
         6 . The method of  claim 1 , wherein the step of determining the least access rate of the least accessed encoded data slice stored in the first memory of the first dispersed storage unit of the plurality of dispersed storage units includes one or more of measuring access rates of encoded data slices stored in the first memory and identifying a minimum access rate. 
     
     
         7 . The method of  claim 1 , wherein the step of determining the estimated access rate for the encoded data slice to be stored includes one or more of identifying the encoded data slice to be stored, measuring an actual access rate and receiving the estimated access rate. 
     
     
         8 . The method of  claim 1  wherein the step of determining whether to store the encoded data slice to be stored in the first memory of the first dispersed storage unit of the plurality of dispersed storage units includes indicating to store the encoded data slice to be stored in the first memory when the estimated access rate is greater than the minimum slice access rate for storing slices in the first memory of the first dispersed storage unit of the plurality of dispersed storage units and the estimated access rate is greater than the least access rate of the least accessed encoded data slice stored in the first memory of the first dispersed storage unit of the plurality of dispersed storage units. 
     
     
         9 . A first dispersed storage unit for use in a dispersed storage network, the dispersed storage network including a plurality of dispersed storage units, the first dispersed storage unit comprising:
 a communications interface;   a first memory;   a second memory;   a computer processor;   where the second memory includes instructions for causing the computer processor to:
 determine a minimum slice access rate for storing slices in the first memory of the first dispersed storage unit of the plurality of dispersed storage units; 
 determine a least access rate of a least accessed encoded data slice stored in the first memory of the first dispersed storage unit of the plurality of dispersed storage units; 
 determine an estimated access rate for an encoded data slice to be stored; 
 determine whether to store the encoded data slice to be stored in the first memory of the first dispersed storage unit of the plurality of dispersed storage units based on the minimum slice access rate for storing slices in the first memory of the first dispersed storage unit of the plurality of dispersed storage units, the least access rate of the least accessed encoded data slice stored in the first memory of the first dispersed storage unit of the plurality of dispersed storage units and the estimated access rate for the encoded data slice to be stored to produce a determination; and 
 store the encoded data slice to be stored in the first memory based on the determination. 
   
     
     
         10 . The first dispersed storage unit of  claim 9 , wherein first memory includes a small fast memory and wherein the second memory includes a large slow memory. 
     
     
         11 . The first dispersed storage unit of  claim 10 , wherein the second memory includes instructions for further causing the computer processor to transfer the encoded data slice from the second memory to the first memory. 
     
     
         12 . The first dispersed storage unit of  claim 9 , wherein the instructions for causing the computer processor to determine the minimum slice access rate for storing slices in the first memory of the first dispersed storage unit of the plurality of dispersed storage units are based on one or more of a historical access rate, a memory wear factor and a capacity level of the first memory. 
     
     
         13 . The first dispersed storage unit of  claim 12 , wherein the memory wear factor includes a maximum number of writes per unit of time. 
     
     
         14 . The first dispersed storage unit of  claim 9 , wherein the second memory includes instructions for further causing the computer processor to, one or more of, measure access rates of encoded data slices stored in the first memory and identify a minimum access rate. 
     
     
         15 . The first dispersed storage unit of  claim 9 , wherein the second memory includes instructions for further causing the computer processor to, one or more, of identify the encoded data slice to be stored, measure an actual access rate and receive the estimated access rate. 
     
     
         16 . The first dispersed storage unit of  claim 9 , wherein the second memory includes instructions for further causing the computer processor to indicate to store the encoded data slice to be stored in the first memory when the estimated access rate is greater than the minimum slice access rate for storing slices in the first memory of the first dispersed storage unit of the plurality of dispersed storage units and the estimated access rate is greater than the least access rate of the least accessed encoded data slice stored in the first memory of the first dispersed storage unit of the plurality of dispersed storage units. 
     
     
         17 . A dispersed storage network comprising:
 a plurality of dispersed storage units;   wherein a first dispersed storage unit of the plurality of dispersed storage units includes:
 a communications interface; 
 a first memory; 
 a second memory; 
 a computer processor;
 where the second memory includes instructions for causing the computer processor to: 
 determine a minimum slice access rate for storing slices in the first memory of the first dispersed storage unit of the plurality of dispersed storage units; 
 determine a least access rate of a least accessed encoded data slice stored in the first memory of the first dispersed storage unit of the plurality of dispersed storage units; 
 determine an estimated access rate for an encoded data slice to be stored; 
 determine whether to store the encoded data slice to be stored in the first memory of the first dispersed storage unit of the plurality of dispersed storage units based on the minimum slice access rate for storing slices in the first memory of the first dispersed storage unit of the plurality of dispersed storage units, the least access rate of the least accessed encoded data slice stored in the first memory of the first dispersed storage unit of the plurality of dispersed storage units and the estimated access rate for the encoded data slice to be stored to produce a determination; and 
 store the encoded data slice to be stored in the first memory based on the determination. 
 
   
     
     
         18 . The dispersed storage network of  claim 17 , wherein first memory includes a small fast memory and the second memory includes a large slow memory. 
     
     
         19 . The dispersed storage network of  claim 18 , wherein the second memory includes instructions for further causing the computer processor to transfer the encoded data slice from the second memory to the first memory. 
     
     
         20 . The dispersed storage network of  claim 17 , wherein the instructions for causing the computer processor to determine the minimum slice access rate for storing slices in the first memory of the first dispersed storage unit of the plurality of dispersed storage units are based on one or more of a historical access rate, a memory wear factor and a capacity level of the first memory.