C# FileStream : Optimal buffer size for writing large files?

Question

Suppose I'm writing a couple of files to disk, between 2MB and 5GB. What are sensible buffer values for the FileStream ?

Is it sensible to work with buffersizes of several megabytes, or should I stick to kilobyte-buffers ?

Answer 1

Default buffer size is 4 KiB.

Also, take a look here: Sequential File Programming Patterns and Performance with .NET

Programming patterns for sequential file access in the .NET Framework are described and the performance is measured. The default behavior provides excellent performance on a single disk – 50 MBps both reading and writing. Using large request sizes and doing file pre-allocation when possible have quantifiable benefits. When one considers disk arrays, .NET unbuffered IO delivers 800 MBps on a 16-disk array, but buffered IO delivers about 12% of that performance. Consequently, high-performance file and database utilities are still forced to use unbuffered IO for maximum sequential performance. The report is accompanied by downloadable source code that demonstrates the concepts and code that was used to obtain these measurements.