ReadFile Kernel32最大缓冲区大小

我使用c#直接从磁盘读取并调用kernel32 ReadFile方法。我注意到，对于较大的读取(目前只读取单个块)，缓冲区大小超出了范围。

有人知道这里读缓冲区的最大大小吗?

如果是这样的话，当我有多余的内存想要读取时，限制缓冲区大小的目的是什么?我理解缓冲和保持较小内存占用的概念，但是为什么我们必须使用较小的内存占用?也许只是一个旧的Win32 API的产物?

编辑:从Marshal.GetLastWin32Error()接收到的错误是"Value does not fall within expected range"。

在我收到此错误之前的上限是8192字节(8KB -因此我感到困惑)。

using System;
using System.IO;
using System.Runtime.InteropServices;
using Microsoft.Win32.SafeHandles;
namespace DiskRead
{
    class Program
    {
        public const uint GenericRead = 0x80000000;
        public const uint FileShareRead = 1;
        public const uint FileShareWrite = 2;
        public const uint OpenExisting = 3;
        [DllImport("kernel32.dll", SetLastError = true, CharSet = CharSet.Unicode)]
        private static extern IntPtr CreateFile(string lpFileName, uint dwDesiredAccess,
          uint dwShareMode, IntPtr lpSecurityAttributes, uint dwCreationDisposition,
          uint dwFlagsAndAttributes, IntPtr hTemplateFile);
        [DllImport("kernel32.dll", SetLastError = true)]
        static extern bool ReadFile(IntPtr hFile, [Out] byte[] lpBuffer,
           uint nNumberOfBytesToRead, out uint lpNumberOfBytesRead, IntPtr lpOverlapped);
        static void Main(string[] args)
        {
            string path = @"''.'PhysicalDrive0";
            IntPtr ptr = CreateFile(path, GenericRead, FileShareRead | FileShareWrite, IntPtr.Zero, OpenExisting, 0, IntPtr.Zero);
            SafeFileHandle handleValue = new SafeFileHandle(ptr, true);
            FileStream fileStream = new FileStream(handleValue, FileAccess.Read);
            const uint numberOfBytesToRead = 8193;
            uint bytesRead;
            byte[] buffer = new byte[numberOfBytesToRead];

            if (!ReadFile(handleValue.DangerousGetHandle(), buffer, numberOfBytesToRead, out bytesRead, IntPtr.Zero))
            {
                Marshal.ThrowExceptionForHR(Marshal.GetHRForLastWin32Error());
            }
        }
    }
}

提前感谢。