filestream threading

Question

Hello,
I'm working on a audio program in C# that is writing binary log data to a SD card on a mobile phone.
It is very important that the audio can run without interruptions.
So I was asking myself if the audio processing will wait for the file being written to the card or if there is rather a standard build-in threading for this in C#, .NET? (so that I don't have to make threads myself...)
I also heard that even when working with threads, it wouldn't be faster then without...?
Thanks for any advice!