Kushai,
It might be a good idea that you visit the following webpage:
Using National Instruments Hardware on Linux. Over there you will general information on how to use NI Hardware in Linux.
Right now, NI also recommends to use the Comedi driver. Follow this link to
Comedi's homepageCOMEDI is a collection of drivers for a variety of common data acquisition plug-in boards. The drivers are implemented as a core Linux kernel module providing common functionality and individual low-level driver modules.
Regarding the sample rate, this should not be affected as long as doing
buffered acquisitions.
Good luck with your application!