Maintenance of a fabric priority during synchronous copy operations

1. A method, comprising:

receiving, by a primary storage controller, a write command from a host, wherein Fibre Channel frames corresponding to the write command have a priority indicated by the host; and

performing, by the primary storage controller, a synchronous copy operation to copy data written by the write command from the primary storage controller to a secondary storage controller, wherein Fibre Channel frames corresponding to the synchronous copy operation have an identical priority to the priority indicated by the host.

2. The method of claim 1 , wherein in a Fibre Connection (FICON) protocol implemented over Fibre Channel, all Fibre Channel frames of all related exchanges pairs that satisfy the write command are set to the identical priority corresponding to the priority indicated by the host.

3. The method of claim 2 , wherein the write command is satisfied by:

a first exchange pair to write the data to the primary storage controller;

a second exchange pair to perform the synchronous copy operation;

a third exchange pair to respond from the primary storage controller to the host that the write command is satisfied, wherein:

Fibre Channel frames of the first exchange pair, the second exchange pair, and the third exchange pair all have the identical priority corresponding to the priority indicated by the host.

4. The method of claim 2 , the method further comprising:

recording the priority of the write command in an input/output (I/O) task control block maintained in the primary storage controller; and

copying the recorded priority to a copy services task control block to transfer the recorded priority for the synchronous copy operation.

5. The method of claim 2 , wherein:

the primary storage controller and the secondary storage controller control a plurality of storage devices; and

a fabric comprising one or more Fibre Channel switches couples the primary storage controller, the secondary storage controller and the host.

6. The method of claim 5 , the method further comprising:

transmitting, by the fabric, the Fibre Channel frames corresponding to the write command according to and with the priority indicated by the host to the primary storage controller; and

transmitting, by the fabric, the Fibre Channel frames corresponding to the synchronous copy operation according to and with the identical priority indicated by the primary storage controller to the secondary storage controller.

7. The method of claim 2 , wherein:

the priority is indicated by programming a CS_CTL/Priority field in a frame headers corresponding to one Fibre Channel frame, and

an exchange pair is comprised of an inbound exchange and an outbound exchange, wherein each of the inbound and the outbound exchange is comprised of one or more sequences, and wherein each sequence is comprised of one or more Fibre Channel frames.

8. A system comprising a primary storage controller, wherein the primary storage controller is coupled to a host and a secondary storage controller, the system comprising:

a memory; and

a processor coupled to the memory, wherein the processor performs operations, the operations comprising:

receiving, by the primary storage controller, a write command from the host, wherein Fibre Channel frames corresponding to the write command have a priority indicated by the host; and

performing, by the primary storage controller, a synchronous copy operation to copy data written by the write command from the primary storage controller to the secondary storage controller, wherein Fibre Channel frames corresponding to the synchronous copy operation have an identical priority to the priority indicated by the host.

9. The system of claim 8 , wherein in a Fibre Connection (FICON) protocol implemented over Fibre Channel, all Fibre Channel frames of all related exchanges pairs that satisfy the write command are set to the identical priority corresponding to the priority indicated by the host.

10. The system of claim 9 , wherein the write command is satisfied by:

a first exchange pair to write the data to the primary storage controller;

a second exchange pair to perform the synchronous copy operation;

a third exchange pair to respond from the primary storage controller to the host that the write command is satisfied, wherein:

Fibre Channel frames of the first exchange pair, the second exchange pair, and the third exchange pair all have the identical priority corresponding to the priority indicated by the host.

11. The system of claim 9 , the operations further comprising:

recording the priority of the write command in an input/output (I/O) task control block maintained in the primary storage controller; and

copying the recorded priority to a copy services task control block to transfer the recorded priority for the synchronous copy operation.

12. The system of claim 9 , wherein:

the primary storage controller and the secondary storage controller control a plurality of storage devices; and

a fabric comprising one or more Fibre Channel switches couples the primary storage controller, the secondary storage controller and the host.

13. The system of claim 12 , the operations further comprising:

transmitting, by the fabric, the Fibre Channel frames corresponding to the write command according to and with the priority indicated by the host to the primary storage controller; and

transmitting, by the fabric, the Fibre Channel frames corresponding to the synchronous copy operation according to and with the identical priority indicated by the primary storage controller to the secondary storage controller.

14. The system of claim 9 , wherein:

the priority is indicated by programming a CS_CTL/Priority field in a frame headers corresponding to one Fibre Channel frame, and

an exchange pair is comprised of an inbound exchange and an outbound exchange, wherein each of the inbound and the outbound exchange is comprised of one or more sequences, and wherein each sequence is comprised of one or more Fibre Channel frames.

15. A computer program product, comprising:

a computer readable storage medium having computer readable program code embodied therewith, the computer readable program code configured to perform operations on a processor, the operations comprising:

receiving, by a primary storage controller, a write command from a host, wherein Fibre Channel frames corresponding to the write command have a priority indicated by the host; and

performing, by the primary storage controller, a synchronous copy operation to copy data written by the write command from the primary storage controller to a secondary storage controller, wherein Fibre Channel frames corresponding to the synchronous copy operation have an identical priority to the priority indicated by the host.

16. The computer program product of claim 15 , wherein in a Fibre Connection (FICON) protocol implemented over Fibre Channel, all Fibre Channel frames of all related exchanges pairs that satisfy the write command are set to the identical priority corresponding to the priority indicated by the host.

17. The computer program product of claim 16 , wherein the write command is satisfied by:

a first exchange pair to write the data to the primary storage controller;

a second exchange pair to perform the synchronous copy operation;

a third exchange pair to respond from the primary storage controller to the host that the write command is satisfied, wherein:

Fibre Channel frames of the first exchange pair, the second exchange pair, and the third exchange pair all have the identical priority corresponding to the priority indicated by the host.

18. The computer program product of claim 16 , the operations further comprising:

recording the priority of the write command in an input/output (I/O) task control block maintained in the primary storage controller; and

copying the recorded priority to a copy services task control block to transfer the recorded priority for the synchronous copy operation.

19. The computer program product of claim 16 , wherein:

the primary storage controller and the secondary storage controller control a plurality of storage devices; and

a fabric comprising one or more Fibre Channel switches couples the primary storage controller, the secondary storage controller and the host.

20. The computer program product of claim 19 , the operations further comprising:

transmitting, by the fabric, the Fibre Channel frames corresponding to the write command according to and with the priority indicated by the host to the primary storage controller; and

transmitting, by the fabric, the Fibre Channel frames corresponding to the synchronous copy operation according to and with the identical priority indicated by the primary storage controller to the secondary storage controller.

21. The computer program product of claim 16 , wherein:

the priority is indicated by programming a CS_CTL/Priority field in a frame headers corresponding to one Fibre Channel frame, and

an exchange pair is comprised of an inbound exchange and an outbound exchange, wherein each of the inbound and the outbound exchange is comprised of one or more sequences, and wherein each sequence is comprised of one or more Fibre Channel frames.