Split beamer notes across multiple notes pages

The closest thing I know is frame overlays, in Beamer a frame can have several overlays (when you use \pause), and you can have different notes for each overlay.

Now this is not exactly what you are asking for. Maybe you can still use this as a workaround, if there's some way to generate "invisible" overlays just for the purpose of adding more notes pages. (Just using pause with no content after it will produce duplicated slides, I guess.)

On the other hand, if you are using this to show the regular slide in one screen and the notes slide in another, what you want is exactly to add several \pauses to have as many overlays as you want, and split your notes through the overlays, so it will still show the same slide when showing the next notes slide.

Like this:

\documentclass[ignorenonframetext,pdfusetitle,17pt]{beamer}
\setbeameroption{show notes}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}

\title{Twitter Architecture}
\author{SA Group 2\\2010 Fall}

\begin{document}
\mode<all>
\begin{frame}{Peaks}
  \textbf{Variable} request rate 
  \pause

  ``\textbf{Constant}'' resources

  \note<2>{Explain the quotes: They can add more machines, but doing
    so as a reaction to rate change is not the same thing. From the
    point of view of random rate changes, resources are constant.}

  \pause

  \textbf{Spread} load over time
  \pause

  How? \textbf{Message Queues}
  \pause
  \note<4>{Twitter controls request rate}
  \pause
  \note<5>{\texttt{(open (get-door 'podbay))}\\
    \texttt{NIL}\\\texttt{(open (get-door 'podbay))}\\
    \texttt{NIL}\\\texttt{(open (get-door 'podbay))}\\
    \texttt{NIL}\\\texttt{(open (get-door 'podbay))}\\
    \texttt{NIL}\\\texttt{(open (get-door 'podbay))}\\
    \texttt{NIL}\\\texttt{(open (get-door 'podbay))}}
  \note<6>{``You can't fight in here!'' -- Merkin Muffley}
\end{frame}
\mode*
\end{document}

I've just found another solution.

\begin{frame}{Slide}
\Huge This is slide
\end{frame}

\note{\Huge Note 1}
\newpage
\note{\Huge Note 2}