Shaping I/O traffic by managing queue depth in fractional increments

1. A method for managing input/output (I/O) traffic in an information handling system, the method comprising:

receiving electronic I/O requests from a network-attached server;

determining a queue depth limit;

monitoring latency of processed electronic I/O requests; and

processing received electronic I/O requests, the processing comprising:

managing a virtual bucket comprising a number of virtual tokens, each token representative of authorization for an I/O request to be processed; and

permitting a received I/O request to be processed if the virtual bucket comprises a number of virtual tokens greater than zero, and decrementing the number of virtual tokens by at least one;

wherein the virtual tokens are added to the virtual bucket at any given time t x according to the equation:

Tokens( t x )=QueueDepthLimit*TimeElapsed( t x −t x-1 )/Latency

wherein Tokens(t x ) gives a value corresponding to a number of virtual tokens to be added to the virtual bucket at time t x ; QueueDepthLimit is the determined queue depth limit; TimeElapsed(t x −t x-1 ) is an amount of time elapsed between time t x and a time t x-1 , where t x-1 is a point in time prior to time t x ; and Latency is a latency of processed electronic I/O requests that have completed during the time elapse between time t x and a time t x-1 .

2. The method of claim 1 , wherein Tokens(t x ) is calculated at periodic intervals.

3. The method of claim 2 , wherein Tokens(t x ) is additionally calculated when an I/O request is received.

4. The method of claim 1 , wherein Tokens(t x ) is calculated at random intervals.

5. The method of claim 1 , wherein Tokens(t x ) is calculated when an I/O request is received.

6. The method of claim 1 , wherein the QueueDepthLimit is a fractional value.

7. The method of claim 1 , wherein processing received I/O requests further comprises waiting to process a received I/O request if the virtual bucket comprises a number of virtual tokens less than zero until the virtual bucket receives additional virtual tokens.

8. A method for managing input/output (I/O) traffic in an information handling system, the method comprising:

receiving electronic I/O requests from a plurality of network-attached servers;

determining a queue depth limit for each of the plurality of network-attached servers;

monitoring latency of processed electronic I/O requests; and

for each of the network-attached servers, processing received electronic I/O requests by:

managing a virtual bucket comprising a number of virtual tokens, each token representative of authorization for an I/O request from at least that network-attached server to be processed; and

permitting a received I/O request from that network-attached server to be processed if the virtual bucket comprises a number of virtual tokens greater than zero, and decrementing the number of virtual tokens by at least one;

wherein the virtual tokens are added to the virtual bucket at any given time t x according to the equation:

Tokens( t x )=QueueDepthLimit*TimeElapsed( t x −t x-1 )/Latency

wherein Tokens(t x ) gives a value corresponding to a number of virtual tokens to be added to the virtual bucket at time t x ; QueueDepthLimit is the determined queue depth limit for that network-attached server; TimeElapsed(t x −t x-1 ) is an amount of time elapsed between time t x and a time t x-1 , where t x-1 is a point in time prior to time t x ; and Latency is a latency of processed electronic I/O requests that have completed during the time elapsed between time t x and a time t x-1 .

9. The method of claim 8 , wherein the queue depth limit for one of the plurality of network-attached servers is different than at least one other of the plurality of network-attached servers.

10. The method of claim 8 , wherein Tokens(t x ) is calculated for each network-attached server when an I/O request is received from that network-attached server.

11. The method of claim 8 , wherein Tokens(t x ) is calculated for each network-attached server at periodic intervals.

12. The method of claim 8 , wherein the QueueDepthLimit for at least one of the network-attached servers is a fractional value.

13. An information handling system comprising:

a data storage system receiving I/O requests from two or more network-attached servers; and a controller managing the data storage system and:

storing a queue depth limit for each of the plurality of network-attached servers;

monitoring latency of processed I/O requests; and

for each of the network-attached servers, processing received I/O requests by:

managing a virtual bucket comprising a number of virtual tokens, each token representative of authorization for an I/O request from at least that network-attached server to be processed; and

permitting a received I/O request from that network-attached server to be processed if the virtual bucket comprises a number of virtual tokens greater than zero, and decrementing the number of virtual tokens by at least one;

wherein the virtual tokens are added to the virtual bucket at any given time t x according to the equation:

Tokens( t x )=QueueDepthLimit*TimeElapsed( t x −t x-1 )/Latency

wherein Tokens(t x ) gives a value corresponding to a number of virtual tokens to be added to the virtual bucket at time t x ; QueueDepthLimit is the determined queue depth limit for that network-attached server; TimeElapsed(t x −t x-1 ) is an amount of time elapsed between time t x and a time t x-1 , where t x-1 is a point in time prior to time t x ; and Latency is a latency of processed electronic I/O requests that have completed during the time elapsed between time t x and a time t x-1 .

14. The information handling system of claim 13 , wherein the queue depth limit for at least one of the plurality of network-attached servers is a fractional value.