Pairing of data storage requests

1. A method performed by a mapping driver of a computing device operating as a data storage system, the method comprising:

receiving, from a storage driver stack, a first data storage command (DSC);

receiving, from the storage driver stack, a second DSC, wherein receiving the second DSC from the storage driver stack includes:

in response to receiving the first DSC, sending a request up the storage driver stack requesting another DSC having a same combined storage command identifier as the first DSC; and

in response to sending the request up the storage driver stack, receiving the second DSC from the storage driver stack, the second DSC having the same combined storage command identifier as the first DSC;

determining that the first DSC and the second DSC are both related aspects of a combined storage command;

in response to determining, establishing a pairing structure to pair the first DSC and the second DSC together; and

fulfilling the combined storage command by fulfilling both the first DSC and the second DSC with reference to the pairing structure.

2. The method of claim 1 wherein the first DSC is received prior to the second DSC and the method further comprises:

successfully completing the combined storage command;

in response to successfully completing, reporting success as response to the first DSC; and

in response to successfully completing, refraining from responding to the second DSC.

3. The method of claim 1 wherein the method further comprises:

receiving a cancellation command directing the data storage system to cancel the combined storage command prior to successfully completing the combined storage command;

in response to receiving the cancellation command, reporting an error as response to the first DSC; and

in response to receiving the cancellation command, reporting an error as response to the second DSC.

4. The method of claim 1 wherein:

the combined storage command is a copy command issued by a remote host instructing the data storage system to copy data from a source location to a destination location;

the first DSC is a source command directing the data storage system to copy from the source location, the source command specifying a source device, a source offset, and a length; and

the second DSC is a destination command directing the data storage system to copy to the destination location, the destination command specifying a destination device and a destination offset.

5. The method of claim 4 wherein establishing the pairing structure includes:

creating a source descriptor structure that specifies the source device, the source offset, and the length;

creating a destination descriptor structure that specifies the destination device and the destination offset;

inserting a reference to the destination descriptor structure within the source descriptor structure; and

inserting a reference to the source descriptor structure within the destination descriptor structure.

6. The method of claim 5 wherein fulfilling the combined storage command includes sending the source descriptor structure and the destination descriptor structure to an I/O Coordination module configured to:

translate the source location from a logical source address to a physical source address; and

translate the destination location from a logical destination address to a physical destination address.

7. The method of claim 4 wherein fulfilling the combined storage command by fulfilling both the first DSC and the second DSC with reference to the pairing structure includes:

translating the source location from a logical source address to a physical source address;

translating the destination location from a logical destination address to a physical destination address; and

sending a copy DSC to a physical storage driver directing the physical storage driver to copy data from the physical source address to the physical destination address, the physical storage driver being able to fulfill the copy DSC without communicating with any driver in the storage driver stack above the mapping driver.

8. The method of claim 1 wherein:

the combined storage command is a mirrored write command issued by a remote host instructing the data storage system to write data to both a first destination location and a second destination location in a mirrored fashion;

the first DSC is a first write command directing the data storage system to write the data to the first destination location, the first write command specifying a first destination device, a first destination offset, and a first length; and

the second DSC is a second write command directing the data storage system to write the data to the second destination location, the second write command specifying a second destination device and a second destination offset.

9. The method of claim 8 wherein fulfilling the combined storage command by fulfilling both the first DSC and the second DSC with reference to the pairing structure includes:

translating the first destination location from a first logical destination address to a first physical destination address;

translating the second destination location from a second logical destination address to a second physical destination address; and

sending a copy DSC to a physical storage driver directing the physical storage driver to copy data from first physical destination address to the second physical destination address, the physical storage driver being able to fulfill the copy DSC without communicating with any driver in the storage driver stack above the mapping driver.

10. A computer program product comprising a non-transitory computer-readable storage medium storing instructions, which, when executed by a computing device cause the computing device to operate a mapping driver of a data storage system by:

receiving, from a storage driver stack, a first data storage command (DSC);

receiving, from the storage driver stack, a second DSC;

determining that the first DSC and the second DSC are both related aspects of a combined storage command;

in response to determining, establishing a pairing structure to pair the first DSC and the second DSC together; and

fulfilling the combined storage command by fulfilling both the first DSC and the second DSC with reference to the pairing structure;

wherein:

the combined storage command is a copy command issued by a remote host instructing the data storage system to copy data from a source location to a destination location;

the first DSC is a source command directing the data storage system to copy from the source location, the source command specifying a source device, a source offset, and a length;

the second DSC is a destination command directing the data storage system to copy to the destination location, the destination command specifying a destination device and a destination offset; and

establishing the pairing structure includes:

creating a source descriptor structure that specifies the source device, the source offset, and the length;

creating a destination descriptor structure that specifies the destination device and the destination offset;

inserting a reference to the destination descriptor structure within the source descriptor structure; and

inserting a reference to the source descriptor structure within the destination descriptor structure.

11. The computer program product of claim 10 wherein fulfilling the combined storage command includes sending the source descriptor structure and the destination descriptor structure to an I/O Coordination module configured to:

translate the source location from a logical source address to a physical source address; and

translate the destination location from a logical destination address to a physical destination address.

12. The computer program product of claim 10 wherein fulfilling the combined storage command by fulfilling both the first DSC and the second DSC with reference to the pairing structure includes:

translating the source location from a logical source address to a physical source address;

translating the destination location from a logical destination address to a physical destination address; and

sending a copy DSC to a physical storage driver directing the physical storage driver to copy data from the physical source address to the physical destination address, the physical storage driver being able to fulfill the copy DSC without communicating with any driver in the storage driver stack above the mapping driver.

13. The computer program product of claim 10 wherein receiving the second DSC from the storage driver stack includes:

in response to receiving the first DSC, sending a request up the storage driver stack requesting another DSC having a same combined storage command identifier as the first DSC; and

in response to sending the request up the storage driver stack, receiving the second DSC from the storage driver stack, the second DSC having the same combined storage command identifier as the first DSC.

14. The computer program product of claim 10 wherein the first DSC is received prior to the second DSC and the instructions, when executed by the computing device cause the computing device to further operate the mapping driver by:

successfully completing the combined storage command;

in response to successfully completing, reporting success as response to the first DSC; and

in response to successfully completing, refraining from responding to the second DSC.

15. The computer program product of claim 10 wherein the instructions, when executed by the computing device cause the computing device to further operate the mapping driver by:

receiving a cancellation command directing the data storage system to cancel the combined storage command prior to successfully completing the combined storage command;

in response to receiving the cancellation command, reporting an error as response to the first DSC; and

in response to receiving the cancellation command, reporting an error as response to the second DSC.

16. An apparatus comprising:

persistent data storage; and

control circuitry coupled to memory configured to execute a mapping driver of a data storage system by:

receiving, from a storage driver stack, a first data storage command (DSC);

receiving, from the storage driver stack, a second DSC;

determining that the first DSC and the second DSC are both related aspects of a combined storage command directed at the persistent data storage;

in response to determining, establishing a pairing structure to pair the first DSC and the second DSC together; and

fulfilling the combined storage command by fulfilling both the first DSC and the second DSC with reference to the pairing structure;

wherein:

the combined storage command is a mirrored write command issued by a remote host instructing the data storage system to write data to both a first destination location and a second destination location in a mirrored fashion;

the first DSC is a first write command directing the data storage system to write the data to the first destination location, the first write command specifying a first destination device, a first destination offset, and a first length; and

the second DSC is a second write command directing the data storage system to write the data to the second destination location, the second write command specifying a second destination device and a second destination offset.

17. The apparatus of claim 16 wherein fulfilling the combined storage command by fulfilling both the first DSC and the second DSC with reference to the pairing structure includes:

translating the first destination location from a first logical destination address to a first physical destination address;

translating the second destination location from a second logical destination address to a second physical destination address; and

sending a copy DSC to a physical storage driver directing the physical storage driver to copy data from first physical destination address to the second physical destination address, the physical storage driver being able to fulfill the copy DSC without communicating with any driver in the storage driver stack above the mapping driver.

18. The apparatus of claim 16 wherein the first DSC is received prior to the second DSC and the control circuitry coupled to memory is further configured to execute the mapping driver by:

successfully completing the combined storage command;

in response to successfully completing, reporting success as response to the first DSC; and

in response to successfully completing, refraining from responding to the second DSC.

19. The apparatus of claim 16 wherein the control circuitry coupled to memory is further configured to execute the mapping driver by:

receiving a cancellation command directing the data storage system to cancel the combined storage command prior to successfully completing the combined storage command;

in response to receiving the cancellation command, reporting an error as response to the first DSC; and

in response to receiving the cancellation command, reporting an error as response to the second DSC.