According to the QLogic FC HBA in an EMC Environment document,
Execution throttle is a HBA parameter that controls the maximum number of I/O commands executing on any one HBA port. When a port’s execution throttle is reached, no new commands are executed until the current command finishes executing…Any more I/O commands will have to wait before they can be scheduled in the HBA. The value of the Execution Throttle parameter can be increased to allow the HBA to execute more commands or decreased to decrease the amount of I/O an HBA port can put on the wire.
This document goes on to show where to change the Execution Throttle setting within the Qlogic SANsurfer GUI. The problem is, this document is a bit dated (July 2007) and that setting is not available in my version of SANsurfer.
I was able to change the Execution Throttle setting by using SANsurfer FC HBA CLI v1.7.1 Build 25. Here’s how I did it:
1. Install SANsurfer CLI
2. Run C:\Program Files\QLogic Corporation\SANsurferCLI\scli.exe
Be patient while the application scans for HBAs
3. From the Main Menu select option 3, HBA Parameters
4. From the HBA Parameters menu select the HBA port you wish to configure.
5. Select option 2, Configure HBA Parameters
6. Select option 11, Execution Throttle Value, which is set to a default of 256. Enter the new value for the Execution Throttle, which can range from 1-65535 and press Enter
7. Select option 19, Commit Changes
8. Select Option 4 to return to the previous menu. Select any additional ports you have in the server, and configure the Execution Throttle to match the new value you just specified.
9. Once you have completed configuring the Execution Throttle, exit out of the SANsurfer CLI program and restart the server so the new changes can take effect.