Question

I’m trying to implement a filecopy method that can match the performance a copy done with the windows explorer.

For exemple a copy (with the windows explorer) from our nas to my computer, performs above 100mb/sec.

My current implementation does the same copy at about 55mb/sec which is already better than the System.IO.File.Copy() which performs at 29mb/sec.

static void Main(string[] args)
    {
        String src = @"";
        String dst = @"";

        Int32 buffersize = 1024 * 1024;
        FileStream input = new FileStream(src, FileMode.Open, FileAccess.Read, FileShare.None, 8, FileOptions.Asynchronous | FileOptions.SequentialScan);
        FileStream output = new FileStream(dst, FileMode.CreateNew, FileAccess.Write, FileShare.None, 8, FileOptions.Asynchronous | FileOptions.SequentialScan);

        Int32 readsize = -1;
        Byte[] readbuffer = new Byte[buffersize];
        IAsyncResult asyncread;
        Byte[] writebuffer = new Byte[buffersize];
        IAsyncResult asyncwrite;

        DateTime Start = DateTime.Now;

        output.SetLength(input.Length);

        readsize = input.Read(readbuffer, 0, readbuffer.Length);
        readbuffer = Interlocked.Exchange(ref writebuffer, readbuffer);

        while (readsize > 0)
        {
            asyncwrite = output.BeginWrite(writebuffer, 0, readsize, null, null);
            asyncread = input.BeginRead(readbuffer, 0, readbuffer.Length, null, null);

            output.EndWrite(asyncwrite);
            readsize = input.EndRead(asyncread);
            readbuffer = Interlocked.Exchange(ref writebuffer, readbuffer);
        }

        DateTime Stop = DateTime.Now;

        TimeSpan Duration = Stop - Start;
        Double speed = input.Length / Duration.TotalSeconds; // bytes/s

        System.Console.WriteLine("MY Speed : " + (speed / 1024 / 1024).ToString() + " mo/sec");

        input.Close();
        output.Close();
        System.IO.File.Delete(dst);
    }

Any idea how to enhance the performance ?

EDIT :

The file is read from a linux-based nas with a 10 Gigabit Ethernet interface with a 60 drives san behind (don’t worry about its performances, it works very well) and written to a local raid0 which can write data at about 140MB/sec.

The bottleneck is the destination’s gigabit network interface which I’m unable to reach with my current code.

Also, removing the write will not make the read any faster, so I can’t go past this 55MB/sec read limit.

EDIT 2 :

The speed issue is related to the fact that the source file is stored on a network share.
Only reading from my local drive with my piece of code provides me a 112MB/sec speed.

EDIT 3 :

Samba doesn’t seem to be the issue. I replaced the cifs share (samba) with a nfs share on my linux nas and got worse results than with samba on my win7 client.

With nfs, my copy method and the windows explorer had the same performance, around 42MB/sec.

I’m out of ideas…

EDIT 4 :

Just to be sure windows was the issue, I’ve installed a debian lenny, mounted my nas trough nfs and got 79MB/sec with the same code under mono.

Answer 1

Probably the only faster option would be using an unbuffered IO: ReadFile Function, CreateFile Function, WriteFile Function with the FILE_FLAG_NO_BUFFERING flag with 2-6 MB buffer.

Also this way you would have to align the buffer size with file system sector size, etc.

It would be significantly faster – especially in Windows XP.

btw. I have achieved ~400 MB bandwidth on a striped RAID 0 array this way (using 4MB buffer).