Method for setting parameters and determining latency in a chained device system

1. A storage system comprising:

a plurality of storage nodes for storing information wherein said plurality of storage nodes are organized in a chained network and at least one of said plurality of storage nodes includes an upstream communication buffer; and

a master controller for controlling flow to said plurality of storage nodes based upon constraints of said upstream communication buffer within said plurality of storage nodes, wherein a communication of a given burst length between said master controller and any of said plurality of storage nodes has a same estimated maximum possible latency, and wherein a maximum possible latency for communication to any storage node is estimated based on:

a minimum latency of a most distant storage node,

a quantity of storage nodes in the plurality of storage nodes, and

a burst length of the communication and a clock period,

wherein said information is independent of an actual latency in a recent read operation, and wherein a minimum possible latency for any storage node other than the most distant storage node is less than the maximum possible latency,

wherein said upstream communication buffer is configured to store a response from a first storage node of the plurality of storage nodes in response to a collision with a response from any downstream storage node of the plurality of storage nodes.

2. A storage system of Claim 1 wherein information on the distribution of said plurality of storage node indicates said plurality of storage nodes are organized in a chained network and priority is given to responses from said storage nodes which are downstream.

3. A storage system of claim 1 wherein a size of at least one of said upstream buffers is established by the length of a burst request in N.

4. A storage system of claim 1 wherein a maximum time that a request from a furthest of said plurality of storage nodes is defined by the relationship:

maxLat(MaxNode)=minLat(MaxNode)+(MaxNode−1)*( BL/ 2*1 /tCK )

where maxLat(MaxNode) is the maximum possible latency of the last node in the chain, minLat(MaxNode) is the minimum latency of the last node in the chain, BL is the burst length of the response and tCK is the clock period.

5. A storage system of claim 4 wherein a minimal latency is determined by the roundtrip time of a request to be sent and a response to be received from a particular one of said plurality of storage nodes as if there were no other requests pending.

6. A storage system of claim 1 wherein said upstream buffer temporarily stores responses from an internal memory core while waiting for responses from other devices downstream to be forwarded upstream.

7. A storage system of claim 1 wherein said master controller estimates an individual latency of a request based upon:

a vector of outstanding responses in said system;

minimum latencies for each of said plurality of storage nodes;

a burst length of the request;

a clock frequency;

a width of a bus coupling said mater controller and said plurality of storage nodes; and

a storage node count of the number of said plurality of storage nodes in said system.

8. A storage method comprising:

obtaining information on a distribution of and traffic flow between a plurality of storage nodes, wherein at least one of said plurality of storage nodes includes an upstream communication buffer;

estimating latency for a responding data request; and

forwarding requests to said plurality of storage nodes based upon said latency information, and wherein a same maximum possible latency for a communication of a given burst length to any of said plurality of storage nodes is estimated based on information of:

a minimum latency of a most distant storage node,

a quantity of storage nodes in the plurality of storage nodes, and

a burst length of the communication and a clock period,

wherein said information is independent of an actual latency in a recent read operation, and wherein a minimum possible latency for any storage node other than the most distant storage node is less than the maximum possible latency,

wherein said upstream communication buffer stores a response from a first storage node of the plurality of storage nodes in response to a collision with a response from any downstream storage node of the plurality of storage nodes.

9. A storage method of claim 8 wherein said information on said distribution indicates said plurality of storage nodes are organized in a chain configuration and priority is given to responses from said memory nodes which are downstream.

10. A storage method of claim 8 wherein said latency includes a dynamic minimal and maximal latency.

11. A storage method of claim 8 wherein said latency includes a latency for a request under constraints.

12. A storage method of claim 8 wherein a minimal latency is determined by the roundtrip time of a request to be sent and a response to be received from a particular one of said plurality of storage nodes as if there were no other requests pending.

13. A storage method of claim 8 wherein a maximal latency is estimated by the time that a request and response from a furthest of said plurality of storage nodes takes to return and is defined by the relationship:

maxLat(MaxNode)=minLat(MaxNode)+(MaxNode−1)*( BL/ 2*1 /tCK )

where maxLat(MaxNode) is the maximum possible latency of the last node in the chain, minLat(MaxNode) is the minimum latency of the last node in the chain, BL is the burst length of the response and tCK is the clock period.

14. A storage method of claim 8 further comprising:

prior to said forwarding said requests, inserting a new request in a vector comprising said requests to be forwarded; and

rearranging said requests to be forwarded and said new request based on corresponding latency of said new request and corresponding latencies of said requests within said vector.

15. A storage method of claim 8 , wherein individual latency of a request is estimated based upon:

a vector of outstanding responses in response to said forwarding requests;

minimum latencies for each of said plurality of storage nodes;

a burst length of the request;

a clock frequency;

a width of a bus; and

a memory node count of the number of said plurality of storage nodes.

16. A storage system comprising:

a first storage node of a plurality of storage nodes for storing information, wherein said first storage node includes an upstream communication buffer; and

a master controller for controlling flow to said first storage node based upon constraints of said communication buffer, wherein a communication of a given burst length between said master controller and any of said plurality of storage nodes has a same estimated maximum possible latency, wherein a response coming from farther downstream of said first storage node is given priority, and wherein the maximum possible latency for any communication to any storage node is estimated based upon:

a minimum latency of a most distant storage node,

a quantity of storage nodes in the storage system, and

a burst length of the communication and a clock period,

wherein said information is independent of an actual latency in a recent read operation, and wherein a minimum possible latency for any storage node other than the most distant storage node is less than the maximum possible latency,

wherein said upstream communication buffer is configured to store a response from said first storage node of the plurality of storage nodes in response to a collision with a response from any downstream storage node of the plurality of storage nodes.

17. A storage system of claim 16 wherein said first storage node and a second storage node are organized in a chain configuration.

18. A storage system of claim 16 , wherein the master controller inserts a new request and rearranges requests within a vector request based on the corresponding latency of said new request and corresponding latencies of said requests within said vector request.