Question

I’ve written the following program which purpose is to create a file of a give size with some random data in it. The program works fine and does what it’s suppose to do. However, I don’t understand why it consumes 5GB of RAM (see screenshot of my Task Manager). While I am writing the file with random data, I am not creating new objects. What am I missing? I would expect this program to take no memory at all.

The big problem I have right now is that in the middle on the file generation, the machine is dying…

class Program
{
    static void Main(string[] args)
    {
        CreateFile("test.dat", 10 * 1024 * 1024);
    }

    public static void CreateFile(string path, long approximativeFileSizeInKb)
    {
        RandomNumberGenerator randomNumber = RandomNumberGenerator.Create();

        byte[] randomData = new byte[64 * 1024];

        int numberOfIteration = 0;
        randomNumber.GetNonZeroBytes(randomData);

        using (FileStream fs = File.Create(path, 64 * 1024))
        {
            while (numberOfIteration++ * 64 < approximativeFileSizeInKb)
            {
                fs.Write(randomData, 0, randomData.Length);
            }
        }
    }
}

Answer 1

Change your line which reads:

using (FileStream fs = File.Create(path, 64 * 1024))

to

using (FileStream fs = File.Create(path, 64 * 1024, FileOptions.WriteThrough))

and see how that does for you.