C# : FTP upload buffer size

问题

I have go that FTP Upload function , but there is something that i want to ask about It is the Buffer size , i set it to 20KB what does it mean and would it make difference if i increased/decreased it ?

    private void Upload(string filename)
    {
        FileInfo fi = new FileInfo(filename);

        FtpWebRequest ftp = (FtpWebRequest)FtpWebRequest.Create("ftp://" + textBox1.Text + "/" + Path.GetFileName(filename));
        ftp.Credentials = new NetworkCredential(textBox2.Text, textBox3.Text);
        ftp.Method = WebRequestMethods.Ftp.UploadFile;
        ftp.UseBinary = true;
        ftp.KeepAlive = false;
        ftp.ContentLength = fi.Length;

        // The buffer size is set to 20kb
        int buffLength = 20480;
        byte[] buff = new byte[buffLength];
        int contentLen;

        //int totalReadBytesCount = 0;

        FileStream fs = fi.OpenRead();

        try
        {
            // Stream to which the file to be upload is written
            Stream strm = ftp.GetRequestStream();

            // Read from the file stream 2kb at a time
            contentLen = fs.Read(buff, 0, buffLength);

            // Till Stream content ends
            while (contentLen != 0)
            {
                // Write Content from the file stream to the 
                // FTP Upload Stream
                strm.Write(buff, 0, contentLen);
                contentLen = fs.Read(buff, 0, buffLength);
            }

            // Close the file stream and the Request Stream
            strm.Close();
            fs.Close();

        }
        catch (Exception ex)
        {
            MessageBox.Show(ex.Message, "Upload Error");
        }
    }

回答1:

For FTP on desktop systems block size of about 256Kb produced the best performance in our tests. Small buffer sizes decrease speed of transfer significantly. I recommend that you do some measurements yourself, but 20Kb is definitely too little for a buffer.

回答2:

Files are already buffered by the file system cache. You should use something lower than 20KB. 4 KB is a traditional choice and I really wouldn't go lower than 4 KB. Don't go below a kilobyte, more than 16 KB is a waste of memory and unfriendly to the CPU's L1 cache (typically 16 or 32 KB of data).

Hans (https://stackoverflow.com/a/3034155)

Use 4 KB (AKA 4096 b)

In .Net 4.5 they increased the default value to 81920 bytes and using the .Net Reflector shows the _DefaultCopyBufferSize has a value of 0x14000 (81920b, or 80K). However, this is for copying from stream to stream, not buffering data. The BufferedStream Class has a _DefaultBufferSize of 0x1000 (4096b or 4k).

来源：https://stackoverflow.com/questions/10871943/c-sharp-ftp-upload-buffer-size

标签

upload

ftp

buffer