Dynamic resource allocation for serial attached SCSI devices
View Patent ↗Various embodiments of the invention provide resource management of available data bandwidth of a SAS system in a non-uniform way. In certain embodiments, arbitration wait time values are adaptively modified to achieve a specified performance quota for a link.
1. A resource allocation controller operable in a storage network, the controller comprising:
a performance measurement element that measures a performance metric on a storage expander within the storage network;
a comparator coupled to the performance measurement element, the comparator compares the measured performance metric to a threshold value and generates a comparison result;
an arbitration wait time (“AWT”) adjustment circuit coupled to the AWT adjustment circuit is configured to dynamically increase and decrease an AWT value based on the comparison result; and
a demand frequency monitoring circuit to detect a demand frequency of an address, wherein the controller sets the threshold value higher in response to detecting an increase in the demand frequency and lower in response to detecting a reduction in the demand frequency.
2. The controller according to claim 1 , wherein the performance metric is representative of a data transfer amount per unit time.
3. The controller according to claim 1 , wherein the threshold value is representative of a device utilization.
4. The controller according to claim 1 , wherein the controller is coupled to a solid state storage device.
5. The controller according to claim 1 , wherein the controller is coupled to a mechanical spinning disk drive.
6. The controller according to claim 1 , wherein the threshold value is programmable.
7. The controller according to claim 1 , the controller receives the threshold value from an out of band communication link.
8. The controller according to claim 1 , the controller receives the threshold value from in band communication link.
9. The controller according to claim 1 , wherein the adjustment circuit further comprises circuitry to load or replace the AWT value into an OPEN frame received by the storage expander in response to the measured performance metric exceeding the threshold value.
10. The controller according to claim 1 , wherein the AWT adjustment circuit further comprises circuitry to increment or decrement the AWT value in response to the measured performance metric exceeding the threshold value.
11. The controller according to claim 1 , wherein the performance measurement element comprises a timer to monitor at least a part of the storage network.
12. The controller according to claim 1 , wherein the performance measurement element is located at a port of the storage expander.
13. The controller according to claim 1 , wherein the performance measurement element is located at a storage end device.
14. The controller according to claim 1 , wherein the controller is located in the storage expander.
15. A method for allocating resources between devices in a storage network, the method comprising:
measuring a performance metric on a storage expander;
comparing the performance metric to a threshold value to generate a comparison result;
dynamically increasing or decreasing an AWT value based on the comparison result that reallocates resources within the storage network;
measuring a demand frequency of an address using a demand frequency monitoring circuit;
comparing the measured demand frequency with the threshold value; and
updating the threshold value.
16. The method according to claim 15 , comprising the step of receiving the threshold value from an Ethernet connection.
17. The method according to claim 15 , wherein the measured performance value is in reference to a specific address.
18. A method for allocating resources between devices in a storage network, the method comprising:
measuring a performance metric on a storage expander;
comparing the performance metric to a threshold value to generate a comparison result; and
increasing an AWT value if the measured performance metric is below the threshold value; and
decreasing the AWT value if the performance metric exceeds the threshold value.
19. A system for allocating resources in a Serial-Attached-SCSI (“SAS”) storage network comprising:
a first storage end device located within the SAS storage network;
a second storage end device located within the SAS storage network, the second storage end device having performance characteristics different from the first storage end device; and
at least one storage expander coupled in the SAS storage network, the at least one storage expander comprising:
a performance measurement element that measures a performance metric within the storage network;
a comparator coupled to receive the measured performance metric, the comparator compares the measured performance metric to a threshold value and generates a comparison result;
an arbitration wait time (“AWT”) adjustment circuit coupled to receive the comparison result, the AWT adjustment circuit dynamically increases and decreases an AWT value based on the comparison result;
a demand frequency monitoring circuit to detect a demand frequency of an address, wherein the controller sets the threshold value higher in response to detecting an increase in the demand frequency and lower in response to detecting a reduction in the demand frequency.
20. The system according to claim 19 , wherein the first storage end device is a solid state storage device and the second storage end device is a mechanical spinning disk drive.