File.Copy vs. Manual FileStream.Write For Copying File

Question

My problem is in regards file copying performance. We have a media management system that requires a lot of moving files around on the file system to different locations inc

Answer 1

Three changes will dramatically improve performance:

1. Increase your buffer size, try 1MB (well -just experiment)
2. After you open your fileStream, call fileStream.SetLength(inStream.Length) to allocate the entire block on disk up front (only works if inStream is seekable)
3. Remove fileStream.Flush() - it is redundant and probably has the single biggest impact on performance as it will block until the flush is complete. The stream will be flushed anyway on dispose.

This seemed about 3-4 times faster in the experiments I tried:

   public static void Copy(System.IO.Stream inStream, string outputFilePath)
    {
        int bufferSize = 1024 * 1024;

        using (FileStream fileStream = new FileStream(outputFilePath, FileMode.OpenOrCreate, FileAccess.Write))
        {
            fileStream.SetLength(inStream.Length);
            int bytesRead = -1;
            byte[] bytes = new byte[bufferSize];

            while ((bytesRead = inStream.Read(bytes, 0, bufferSize)) > 0)
            {
                fileStream.Write(bytes, 0, bytesRead);
            }
       }
    }