Writing/Reading Speed issues (c#)

Hello everyone!
I had serious problems with speed of writing and reading in c#. Ive done tests (look at NI.jpg) and speed of writing is about 2 sec, and reading about 7-8 sec. 

Its a disaster for my project. This is a peice of my code of reading:

double[] PV=firstchannelsInterpol[0].GetData<double>();
double[] SP = firstchannelsInterpol[1].GetData<double>();
double[] OP = firstchannelsInterpol[2].GetData<double>();
double[] OPmin = firstchannelsInterpol[3].GetData<double>();
double[] OPmax = firstchannelsInterpol[4].GetData<double>();
double[] PVmin = firstchannelsInterpol[5].GetData<double>();
double[] PVmax = firstchannelsInterpol[6].GetData<double>();
Int32[] Mode = firstchannelsInterpol[7].GetData<Int32>();
string[] Time = firstchannelsInterpol[8].GetData<string>();

Am I doing smth wrong?
Thanks