1 . A method for managing a storage device, comprising: in response to receiving an I/O request for a storage device comprising a plurality of disks, determining, from the plurality of disks, at least one disk related to the I/O request; allocating, to each of the at least one disk, at least one access credit for completing the I/O request from total access credits of the disk, wherein the total access credits are associated with at least one of a type of the disk, a type of the I/O request and performance of the disk; and in response to respective access credits being allocated to the at least one disk, performing access requested by the I/O request to each of the at least one disk.
2 . The method of claim 1 , wherein allocating the at least one access credit comprises: determining, based on the type of the I/O request, the total access credits of the disk; determining whether the total access credits are sufficient for completing the I/O request; and in response to the total access credits being sufficient for completing the I/O request, allocating the at least one access credit from the total access credits.
3 . The method of claim 2 , wherein determining the total access credits comprises: in response to the I/O request being a read request, determining the total access credits as read access credits for read requests, wherein the read access credits indicate a maximum number of read requests which can be processed by the disk simultaneously; and in response to the I/O request being a write request, determining the total access credits as write access credits for write requests, wherein the write access credits indicate a maximum number of write requests which can be processed by the disk simultaneously.
4 . The method of claim 2 , wherein determining the total access credits comprises: determining the total access credits as hybrid access credits for read requests or write requests, wherein the hybrid access credits indicate a maximum value of a total number of read requests and write requests which can be processed by the disk simultaneously.
5 . The method of claim 1 , further comprising: in response to the at least one access credit failing to be allocated to one of the at least one disk, reclaiming access credits having been allocated for the I/O request; and suspending allocation of access credits for the I/O request until an access credit allocated for a previous I/O request directed to the storage device is reclaimed.
6 . The method of claim 1 , further comprising: in response to respective access to the at least one disk being completed, reclaiming the respective access credits allocated to the at least one disk for a subsequent I/O request.
7 . The method of claim 1 , further comprising: determining a response time of the disk to the I/O request; determining a time interval between a current time and a most recent time at which the total access credits of the disk are adjusted; and in response to the time interval exceeding a predetermined threshold, adjusting the total access credits of the disk based on the response time.
8 . The method of claim 7 , wherein adjusting the total access credits of the disk comprises: in response to the response time exceeding a first threshold, decreasing the total access credits of the disk; and in response to the response time being lower a second threshold, increasing the total access credits of the disk, wherein the first threshold exceeds the second threshold.
9 . The method of claim 1 , wherein the initial number of the total access credits of the disk is associated with a type of the disk, and wherein the initial number of total access credits of a disk having a first type associated with higher performance exceeds the initial number of total access credits of a disk having a second type associated with lower performance.
10 . The method of claim 3 , wherein the initial number of the read access credits exceeds that of the write access credits.
11 . The method of claim 1 , wherein the storage device is a Redundant Array of Independent Disks (RAID).
12 . An apparatus for managing a storage device, comprising: at least one processing unit; at least one memory coupled to the at least one processing unit and storing instructions for execution by the at least one processing unit, the instructions, when executed by the at least one processing unit, causing the apparatus to perform actions comprising: in response to receiving an I/O request for a storage device comprising a plurality of disks, determining, from the plurality of disks, at least one disk related to the I/O request; allocating, to each of the at least one disk, at least one access credit for completing the I/O request from total access credits of the disk, wherein the total access credits are associated with at least one of a type of the disk, a type of the I/O request and performance of the disk; and in response to respective access credits being allocated to the at least one disk, performing access requested by the I/O request to each of the at least one disk.
13 . The apparatus of claim 12 , wherein allocating the at least one access credit comprises: determining, based on the type of the I/O request, the total access credits of the disk; determining whether the total access credits are sufficient for completing the I/O request; and in response to the total access credits being sufficient for completing the I/O request, allocating the at least one access credit from the total access credits.
14 . The apparatus of claim 13 , wherein determining the total access credits comprises: in response to the I/O request being a read request, determining the total access credits as read access credits for read requests, wherein the read access credits indicate a maximum number of read requests which can be processed by the disk simultaneously; and in response to the I/O request being a write request, determining the total access credits as write access credits for write requests, wherein the write access credits indicate a maximum number of write requests which can be processed by the disk simultaneously.
15 . The apparatus of claim 13 , wherein determining the total access credits comprises: determining the total access credits as hybrid access credits for read requests or write requests, wherein the hybrid access credits indicate a maximum value of a total number of read requests and write requests which can be processed by the disk simultaneously.
16 . The apparatus of claim 12 , wherein the actions further comprise: in response to the at least one access credit failing to be allocated to one of the at least one disk, reclaiming access credits having been allocated for the I/O request; and suspending allocation of access credits for the I/O request until an access credit allocated for a previous I/O request directed to the storage device is reclaimed.
17 . The apparatus of claim 12 , wherein the actions further comprise: in response to respective access to the at least one disk being completed, reclaiming the respective access credits allocated to the at least one disk for a subsequent I/O request.
18 . The apparatus of claim 12 , wherein the actions further comprise: determining a response time of the disk to the I/O request; determining a time interval between a current time and a most recent time at which the total access credits of the disk are adjusted; and in response to the time interval exceeding a predetermined threshold, adjusting the total access credits of the disk based on the response time.
19 . The apparatus of claim 18 , wherein adjusting the total access credits of the disk comprises: in response to the response time exceeding a first threshold, decreasing the total access credits of the disk; and in response to the response time being lower a second threshold, increasing the total access credits of the disk, wherein the first threshold exceeds the second threshold.
20 . The apparatus of claim 12 , wherein the initial number of the total access credits of the disk is associated with a type of the disk, and wherein the initial number of total access credits of a disk having a first type associated with higher performance exceeds the initial number of total access credits of a disk having a second type associated with lower performance.
21 . The apparatus of claim 14 , wherein the initial number of the read access credits exceeds that of the write access credits.
22 . The apparatus of claim 12 , wherein the storage device is a Redundant Array of Independent Disks (RAID).
23 . A computer program product having a non-transitory computer readable medium which stores a set of instructions to manage a storage device; the set of instructions, when carried out by computerized circuitry, causing the computerized circuitry to perform a method of: in response to receiving an I/O request for a storage device comprising a plurality of disks, determining, from the plurality of disks, at least one disk related to the I/O request; allocating, to each of the at least one disk, at least one access credit for completing the I/O request from total access credits of the disk, wherein the total access credits are associated with at least one of a type of the disk, a type of the I/O request and performance of the disk; and in response to respective access credits being allocated to the at least one disk, performing access requested by the I/O request to each of the at least one disk.
