\begin{slide}{violet}
\violet
\begin{center}
Disk Scheduling Algorithms
\end{center}
\begin{itemize}
\item heavy load $\rightarrow$ good scheduling can reduce mean waiting time
50\% (cmp. FCFS)
\item current overall winner: WSCAN (Suggs)
\begin{itemize}
\item maintain current read/write head direction (in or out)
\item serve next the closest request in current direction, unless
there's a request in ``window'' behind head (if so, get it)
\item if no requests in current direction, change direction
\end{itemize}
WSCAN tested by Data General: will appear in future release of DG/UX
\end{itemize}
\end{slide}


