fast copy array c#

public unsafe struct MyStruct //the actual struct used, contains all
{
    public int a;
    public unsafe fixed byte buffer[16];
    public ulong b;
    //etc.
}

public unsafe struct FixedSizeBufferWrapper //contains _only_ the buffer
{
    public unsafe fixed byte buffer[16];
}

unsafe 
{
    fixed (byte* bufferA = myStructA.buffer, bufferB = myStructB.buffer)
    {
        *((FixedSizeBufferWrapper*)bufferA) =
        *((FixedSizeBufferWrapper*)bufferB);
    }
}

int[] a = new int[] {1,2,3,4,5,6,7,8};
  int[] b = new int[a.Length];
  int size = sizeof(int);
  int length = a.Length * size;               
  System.Buffer.BlockCopy(a, 0, b, 0, length);