Methods and devices for determining quality of services of storage systems

Abstract

Methods and systems for allowing access to computer storage systems. Multiple requests from multiple applications can be received and processed efficiently to allow traffic from multiple customers to access the storage system concurrently.

1 . A method for providing access to a storage system, the method comprising:
 (a) receiving a plurality of requests from a plurality of applications for access to the storage system;   (b) assigning each application to one of a plurality of queues;   (c) calculating an initial quanta for each queue;   (d) selecting a first queue to access the storage system so that a request from the first queue can be serviced by the storage system;   (e) calculating a subsequent quanta for the first queue after the request from the first queue has been serviced by the storage system;   (f) determining if the subsequent quanta for the first queue is greater than or less than a predetermined value;   (g) selecting the first queue to access the storage system if the subsequent quanta for the first queue is greater than the predetermined value, so that a subsequent request from the first queue can be serviced by the storage system; and   (h) selecting a second queue to access the storage system if the subsequent quanta for the first queue is less than the predetermined value, so that a request from the second queue can be serviced by the storage system.   
     
     
         2 . The method of  claim 1  wherein steps (c) through (g) are repeated until the subsequent quanta for the first queue is less than the predetermined value. 
     
     
         3 . The method of  claim 2  further comprising:
 (i) calculating a subsequent quanta for the second queue after the request from the second queue has been serviced by the storage system; 
 (j) determining if the subsequent quanta for the second queue is greater than or less than the predetermined value; 
 (k) selecting the second queue to access the storage system if the subsequent quanta for the second queue is greater than the predetermined value, so that a subsequent request from the second queue can be serviced by the storage system; and 
 (l) selecting the first queue to access the storage system if the subsequent quanta for the second queue is less than the predetermined value, so that a request from the first queue can be serviced by the storage system. 
 
     
     
         4 . The method of  claim 3  wherein the subsequent quanta for the first queue is less than the predetermined value by a specific amount in a round, and wherein the specific amount is subtracted from the subsequent quanta for the first queue in a subsequent round. 
     
     
         5 . The method of  claim 3  wherein the subsequent quanta for the second queue is less than the predetermined value by a specific amount in a round, and wherein the specific amount is subtracted from the subsequent quanta for the second queue in a subsequent round. 
     
     
         6 . The method of  claim 1  wherein the predetermined value is zero. 
     
     
         7 . The method of  claim 1  wherein each of the applications has a weight and the initial quanta calculated for each queue is based on the weight of the application. 
     
     
         8 . The method of  claim 1 , where the plurality of requests for access to the storage system are received concurrently. 
     
     
         9 . The method of  claim 1 , where a service time for the first queue to access the storage system does not affect the service time for the second queue to access the storage system. 
     
     
         10 . A method comprising:
 receiving a plurality of requests for access to the storage system;   receiving a plurality of priorities for each of the requesting applications;   calculating a quanta for each of a plurality of queues;   selecting a queue to access the storage system;   calculating the quanta left after the selected queue accesses the storage system;   selecting a next queue for access to storage; and   utilizing a virtual input/output scheduler and a plurality of application-dependent schedulers to allocate a first portion of the available service time to the first request and to allocate a second portion of the available service time to the second request.   
     
     
         11 . The method of  claim 10 , where the first portion and the second portion are in proportion to an assigned weight for each of the queues. 
     
     
         12 . The method of  claim 10 , where the first queue has a request to obtain a first amount of data, the second queue has a request to obtain a second amount of data, and each queue has its own application-specific scheduler. 
     
     
         13 . The method of  claim 10 , where the virtual input/output scheduler allocates service to the first and second queues in a round-robin fashion. 
     
     
         14 . The method of  claim 10 , where a service time calculation for the first request for access to the storage system does not affect a service time calculation for the second request for access to the storage system.