Method and apparatus for balancing workloads among paths in a multi-path computer system based on the state of previous I/O operations

Claim 3

The method of claim 1 , wherein each of the at least two paths includes a transmission medium, and wherein the step (A) includes a step of selecting the one of the at least two paths based upon at least one characteristic of the transmission media used to implement the at least two paths.

Claim 4

The method of claim 1 , wherein each of the at least two paths includes a transmission medium, wherein the transmission media used to implement the at least two paths are different, and wherein the step (A) includes a step of selecting the one of the at least two paths based upon data transmission rates through the transmission media used to implement the at least two paths.

Claim 5

The method of claim 3 , wherein the step (A) includes a step of selecting the one of the at least two paths based upon arbitration times for the transmission media used to implement the at least two paths.

Claim 6

The method of claim 2 , wherein each of the at least two paths includes a transmission medium, wherein the transmission media used to implement the at least two paths are different, and wherein the step (A) includes a step of selecting the one of the at least two paths based upon arbitration times for the transmission media used to implement the at least two paths.

Claim 7

The method of claim 2 , wherein each I/O operation has an associated data access time when processed by the system resource, and wherein the step (A) includes a step of selecting the one of the at least two paths based upon the data access times of the previously assigned I/O operations queued to the at least two paths.

Claim 8

The method of claim 6 , wherein the system resource includes at least one storage system, wherein reads from and writes to the storage system have different average data access times, and wherein the step (A) includes a step of selecting the one of the at least two paths based upon a number of reads and writes in the previously assigned I/O operations queued to the at least two paths.

Claim 11

The method of claim 8 , wherein the I/O operations are executed as part of an application program on the host computer, and wherein the method further includes a step of estimating the number of cache hits and cache misses in the previously assigned I/O operations queued to the at least two paths based upon historical performance of the application program.

Claim 12

The method of claim 9 , wherein each of the I/O operations is directed to a particular target device in the storage system, and wherein the step (A) includes a step of selecting the one of the at least two paths based upon the target device of the next I/O operation.

Claim 13

The method of claim 10 , wherein the step of selecting the one of the at least two paths based upon the target device of the next I/O operation includes a step of considering whether the previously assigned I/O operations queued to the at least two paths are directed to a same target device as the next I/O operation.

Claim 14

The method of claim 11 , wherein the step of selecting the one of the at least two paths based upon the target device of the next I/O operation includes a step of limiting a number of the at least two paths to which a plurality of I/O operations directed to a single target device are queued simultaneously.

Claim 15

The method of claim 12 , wherein the step of limiting the number of the multiple paths to which a plurality of I/O operations directed to the single target device are queued simultaneously includes a step of limiting the number of the at least two paths to a minimum number that achieves a bandwidth through the at least two paths that maximizes performance of the storage system for the target device.

Claim 16

The method of claim 13 , wherein the I/O operations are executed as part of an application program on the host computer, and wherein the step (A) includes a step of selecting the one of the at least two paths based upon a priority rating for the next I/O operation, the priority rating relating to an impact that the next I/O operation has on the performance of the application program.

Claim 17

The method of claim 14 , wherein the step of selecting the one of the at least two paths based upon the priority rating for the next I/O operation includes a step of: when the next I/O operation is critical to the performance of the application program, selecting the one of the at least two paths that is expected to be the shortest path to execute the next I/O operation.

Claim 18

The method of claim 15 , wherein the step of selecting the one of the at least two paths based upon the priority rating for the next I/O operation includes a step of: when the next I/O operation is not critical to the performance of the application program, selecting the one of the at least two paths to be one of the at least two paths that is expected to not be the shortest path to execute the next I/O operation.

Claim 19

The method of claim 1 , wherein each of the I/O operations queued for transmission over the at least two paths includes a number of data blocks for transmission between the host computer and the system resource, and wherein the step (A) includes a step of selecting the one of the at least two paths based upon a number of data blocks included in the previously assigned I/O operations queued to each of the at least two paths.

Claim 22

The method of claim 18 , wherein the step of selecting the one of the at least two paths based upon the target device of the next I/O operation includes a step of considering whether the previously assigned I/O operations queued to the at least two paths are directed to a same target device as the next I/O operation.

Claim 23

The method of claim 18 , wherein the step of selecting the one of the at least two paths based upon the target device of the next I/O operation includes a step of limiting a number of the at least two paths to which a plurality of I/O operations directed to a single target device are queued simultaneously.

Claim 24

A host computer capable of use in a multi-path computer system including a system resource and a plurality of paths coupling the host computer to the system resource, the host computer comprising: a driver to distribute input/output (I/O) operations initiated by the host computer among at least two of the plurality of paths for transmission to the system resource, the driver selecting, for a next I/O operation to be assigned for transmission from the host computer to the system resource, one of the at least two paths based upon a state of previously assigned I/O operations queued for transmission to the system resource over the at least two of the plurality of paths; wherein each I/O operation has an associated data access time when processed by the system resource, and wherein the driver selects the one of the at least two of the plurality of paths based upon the data access times of the previously assigned I/O operations queued to the at least two of the plurality of paths; and wherein the system resource is a storage system including a cache, wherein cache hits and cache misses have different average data access times in the storage system, and wherein the driver selects the one of the at least two of the plurality of paths based upon a number of estimated cache hits and cache misses in the previously assigned I/O operations queued to the at least two of the plurality of paths.

Claim 25

A host computer capable of use in a multi-path computer system including a system resource and a plurality of paths coupling the host computer to the system resource, the host computer comprising: a driver to distribute input/output (I/O) operations initiated by the host computer among at least two of the plurality of paths for transmission to the system resource, the driver selecting, for a next I/O operation to be assigned for transmission from the host computer to the system resource, one of the at least two paths based upon a state of previously assigned I/O operations queued for transmission to the system resource over the at least two of the plurality of paths; wherein each I/O operation has an associated data access time when processed by the system resource, and wherein the driver selects the one of the at least two of the plurality of paths based upon the data access times of the previously assigned I/O operations queued to the at least two of the plurality of paths; and wherein the system resource is a storage system including a cache, wherein cache hits and cache misses have different average data access times in the storage system, and wherein the driver selects the one of the at least two of the plurality of paths based upon a number of estimated cache hits and cache misses in the previously assigned I/O operations queued to the at least two of the plurality of paths.

Claim 26

The host computer of claim 21 , wherein each of the at least two of the plurality of paths includes a transmission medium, and wherein the driver selects the one of the at least two of the plurality of paths based upon at least one characteristic of the transmission media used to implement the at least two of the plurality of paths.

Claim 27

The host computer of claim 21 , wherein each of the at least two of the plurality of paths includes a transmission medium, wherein the transmission media used to implement the at least two of the plurality of paths are different, and wherein the driver selects the one of the at least two of the plurality of paths based upon a data transmission rate through the transmission media used to implement the at least two of the plurality of paths.

Claim 28

The host computer of claim 23 , wherein the driver selects the one of the at least two of the plurality of paths based upon an arbitration time for the transmission media used to implement the at least two of the plurality of paths.

Claim 29

The host computer of claim 22 , wherein each of the at least two of the plurality of paths includes a transmission medium, wherein the transmission media used to implement the at least two of the plurality of paths are different, and wherein the driver selects the one of the at least two of the plurality of paths based upon an arbitration time for the transmission media used to implement the at least two of the plurality of paths.

Claim 30

The host computer of claim 22 , wherein each I/O operation has an associated data access time when processed by the system resource, and wherein the driver selects the one of the at least two of the plurality of paths based upon the data access times of the previously assigned I/O operations queued to the at least two of the plurality of paths.

Claim 31

The host computer of claim 26 , wherein the system resource includes at least one storage system, wherein reads from and writes to the storage system have different average data access times, and wherein the driver selects the one of the at least two of the plurality of paths based upon a number of reads and writes in the previously assigned I/O operations queued to the at least two of the plurality of paths.

Claim 32

A host computer capable of use in a multi-path computer system including a system resource and a plurality of paths coupling the host computer to the system resource, the host computer comprising: a driver to distribute input/output (I/O) operations initiated by the host computer among at least two of the plurality of paths for transmission to the system resource, the driver selecting, for a next I/O operation to be assigned for transmission from the host computer to the system resource, one of the at least two paths based upon a state of previously assigned I/O operations queued for transmission to the system resource over the at least two of the plurality of paths; wherein the driver selects the one of the at least two of the plurality of paths based upon a number of previously assigned I/O operations queued to each of the at least two of the plurality of paths; wherein each of the I/O operations queued for transmission over the at least two of the plurality of paths includes a number of data blocks for transmission between the host computer and the system resource, and wherein the driver selects the one of the at least two of the plurality of paths based upon a number of data blocks included in the previously assigned I/O operations queued to each of the at least two of the plurality of paths; wherein each of the at least two of the plurality of paths includes a transmission medium, and wherein the driver selects the one of the at least two of the plurality of paths based upon at least one characteristic of the transmission media used to implement the at least two of the plurality of paths; wherein each I/O operation has an associated data access time when processed by the system resource, and wherein the driver selects the one of the at least two of the plurality of paths based upon the data access times of the previously assigned I/O operations queued to the at least two of the plurality of paths; and wherein the system resource includes at least one storage system including a cache, wherein cache hits and cache misses have different average data access times in the storage system, and wherein the driver selects the one of the at least two of the plurality of paths based upon a number of estimated cache hits and cache misses in the previously assigned I/O operations queued to the at least two of the plurality of paths.

Claim 33

A host computer capable of use in a multi-path computer system including a system resource and a plurality of paths coupling the host computer to the system resource, the host computer comprising: a driver to distribute input/output (I/O) operations initiated by the host computer among at least two of the plurality of paths for transmission to the system resource, the driver selecting, for a next I/O operation to be assigned for transmission from the host computer to the system resource, one of the at least two paths based upon a state of previously assigned I/O operations queued for transmission to the system resource over the at least two of the plurality of paths; wherein the driver selects the one of the at least two of the plurality of paths based upon a number of previously assigned I/O operations queued to each of the at least two of the plurality of paths; wherein each of the I/O operations queued for transmission over the at least two of the plurality of paths includes a number of data blocks for transmission between the host computer and the system resource, and wherein the driver selects the one of the at least two of the plurality of paths based upon a number of data blocks included in the previously assigned I/O operations queued to each of the at least two of the plurality of paths; wherein each of the at least two of the plurality of paths includes a transmission medium, and wherein the driver selects the one of the at least two of the plurality of paths based upon at least one characteristic of the transmission media used to implement the at least two of the plurality of paths; wherein each I/O operation has an associated data access time when processed by the system resource, and wherein the driver selects the one of the at least two of the plurality of paths based upon the data access times of the previously assigned I/O operations queued to the at least two of the plurality of paths; and wherein the system resource includes at least one storage system including a cache, wherein cache hits and cache misses have different average data access times in the storage system, and wherein the driver selects the one of the at least two of the plurality of paths based upon a number of estimated cache hits and cache misses in the previously assigned I/O operations queued to the at least two of the plurality of paths.

Claim 34

The host computer of claim 28 , wherein the I/O operations are executed as part of an application program on the host computer, and wherein the driver estimates the number of cache hits and cache misses in the previously assigned I/O operations queued to the at least two of the plurality of paths based upon historical performance of the application program.

Claim 35

The host computer of claim 29 , wherein each of the I/O operations is directed to a particular target device in the storage system, and wherein the driver selects the one of the at least two of the plurality of paths based upon the target device of the next I/O operation.

Claim 36

The host computer of claim 30 , wherein the driver considers whether the previously assigned I/O operations queued to the at least two of the plurality of paths are directed to a same target device as the next I/O operation.

Claim 37

The host computer of claim 31 , wherein the driver limits a number of the at least two of the plurality of paths to which a plurality of I/O operations directed to a single target device are queued simultaneously.

Claim 38

The host computer of claim 32 , wherein the driver limits the number of the at least two of the plurality of paths to a minimum number that achieves a bandwidth through the at least two of the plurality of paths that maximizes performance of the storage system for the target device.

Claim 39

The host computer of claim 33 , wherein the I/O operations are executed as part of an application program on the host computer, and wherein the driver selects the one of the at least two of the plurality of paths based upon a priority rating for the next I/O operation, the priority rating relating to an impact that the next I/O operation has on the performance of the application program.

Claim 40

The host computer of claim 34 , wherein when the next I/O operation is critical to the performance of the application program, the driver selects the one of the at least two of the plurality of paths that is expected to be the shortest path to execute the next I/O operation.

Claim 41

The host computer of claim 35 , wherein when the next I/O operation is not critical to the performance of the application program, the driver selects the one of the at least two of the plurality of paths to be one of the at least two of the plurality of paths that is expected to not be the shortest path to execute the next I/O operation.

Claim 42

The host computer of claim 21 , wherein each of the I/O operations queued for transmission over the at least two of the plurality of paths includes a number of data blocks for transmission between the host computer and the system resource, and wherein the driver selects the one of the at least two of the plurality of paths based upon a number of data blocks included in the previously assigned I/O operations queued to the at least two of the plurality of paths.

Claim 43

A host computer capable of use in a multi-path computer system including a system resource and a plurality of paths coupling the host computer to the system resource, the host computer comprising: a driver to distribute input/output (I/O) operations initiated by the host computer among at least two of the plurality of paths for transmission to the system resource, the driver selecting, for a next I/O operation to be assigned for transmission from the host computer to the system resource, one of the at least two paths based upon a state of previously assigned I/O operations queued for transmission to the system resource over the at least two of the plurality of paths; wherein each of the I/O operations is directed to a particular target device in the system resource, and wherein the driver selects the one of the at least two of the plurality of paths based upon the target device of the next I/O operation.

Claim 44

A host computer capable of use in a multi-path computer system including a system resource and a plurality of paths coupling the host computer to the system resource, the host computer comprising: a driver to distribute input/output (I/O) operations initiated by the host computer among at least two of the plurality of paths for transmission to the system resource, the driver selecting, for a next I/O operation to be assigned for transmission from the host computer to the system resource, one of the at least two paths based upon a state of previously assigned I/O operations queued for transmission to the system resource over the at least two of the plurality of paths; wherein each of the I/O operations is directed to a particular target device in the system resource, and wherein the driver selects the one of the at least two of the plurality of paths based upon the target device of the next I/O operation.

Claim 45

The host computer of claim 38 , wherein the driver considers whether the previously assigned I/O operations queued to the at least two of the plurality of paths are directed to a same target device as the next I/O operation.

Claim 46

The host computer of claim 38 , wherein the driver limits a number of the at least two of the plurality of paths to which a plurality of I/O operations directed to a single target device are queued simultaneously.

Claim 47

The host computer of claim 21 , wherein the driver includes means for selecting the one of the at least two of the plurality of paths based upon the state of previously assigned I/O operations queued for transmission to the system resource over the at least two of the plurality of paths.

Claim 48

The host computer of claim 21 , wherein the host computer includes a processor, and wherein the driver is a software driver executing on the processor.

Claim 49

The host computer of claim 21 , in combination with the system resource and the multiple paths to form the multi-path computer system.

Claim 50

A computer readable medium encoded with a program that, when executed on a host computer, performs the method according to claim 2 .

Claim 51

The host computer of claim 28 , in combination with the system resource and the multiple paths to form the multi-path computer system.

Claim 52

The host computer of claim 38 , in combination with the system resource and the multiple paths to form the multi-path computer system.

Claim 53

The host computer of claim 21 , in combination with the system resource and the multiple paths to form the multi-path computer system.

Claim 54

A computer readable medium encoded with a program that, when executed on a host computer, performs the method according to claim 8 .

Claim 55

A computer readable medium encoded with a program that, when executed on a host computer, performs the method according to claim 18 .

Claim 56

A computer readable medium encoded with a program that, when executed on a host computer, performs the method according to claim 1 .