In our QSF file below mentioned by earlier Fpga engineers :
Now we have mix of 2.5V, 1.8V and 3.3V now
set_global_assignment -name STRATIX_DEVICE_IO_STANDARD "2.5 V"
should we remove this statement from qsf file ? our quartus version is 9.0 sp2 .
No, you shouldnt if you have 2.5V I/O standard in your design. Moreover, it is not recommended to modify QSF file if you are setting the I/O in pin planner.