The maximum SCSI queue depth value, as determined by the Microsoft port driver developer, is 254. QLogic sets the default value to 32. The Microsoft storport.sys driver has total control of the depth of the device queue; QLogic Miniport merely sets the value using the predefined Storport interface call and procedure as determined by Microsoft.
Use the following procedure to change the queue depth parameter:
Start, select Run, and open the REGEDIT/REGEDT32 program.
HKEY_LOCAL_MACHINE and follow the tree structure down to the QLogic driver as follows:
3. Double-click DriverParameter to edit the string, for example:
DriverParameter REG_SZ qd=32
4. Add "qd=" to the "Value data:" field. If the string "qd=" does not exist, append it to end of the string with a semicolon, for example:
5. Enter a value up to 254 (0xFE).
The default value is 32 (0x20).
6. Click OK.
7. Exit the Registry Editor, then shutdown and reboot the system.