\section{RAID Levels}

\begin{frame}
   {RAID Levels}

   \begin{itemize}
      \item \textbf{RAID 0}: striping
      \item \textbf{RAID 1}: mirroring
      \item \textbf{RAID 5}: striping with distributed parity
      \item \textbf{RAID 6}: striping with dual distributed parity
      \item \textbf{RAID 10}: mirrored and striped
      \item \textbf{RAID} levels can be combined
   \end{itemize}

\end{frame}

\cprotect\note{


   There are a number of \textbf{RAID} specifications of
   increasing complexity and use. The most commonly used are
   levels 0, 1, and 5.
   \begin{itemize}
      \item
      \textbf{RAID 0} uses only striping. Data is spread across
      multiple disks. However, in spite of the name, there is
      no redundancy and there is no stability or recovery
      capabilities. In fact, if any disk fails data will be
      lost. But performance can be improved significantly
      because of parallelization of I/O tasks.
      \item
      \textbf{RAID 1} uses only mirroring; each disk has a
      duplicate. This is good for recovery. At least two disks
      are required.
      \item
      \textbf{RAID 5} uses a rotating parity stripe; a single
      drive failure will cause no loss of data, only a
      performance drop. There must be at least 3 disks.
      \item
      \textbf{RAID 6} has striped disks with dual parity; it
      can handle loss of two disks, and requires at least 4
      disks. Because \textbf{RAID 5} can impose significant
      stress on disks, which can lead to failures during
      recovery procedures, \textbf{RAID 6} has become more
      important.
      \item
      \textbf{RAID 10} is a mirrored and striped data set. At
      least 4 drives are needed.
   \end{itemize}
   As a general rule adding more disks improves
   performance.
}




