\section{Logical Volume Management (LVM)}

\begin{frame}
   {LVM}

   \begin{itemize}
      \item Multiple disks grouped together to create
      volumes
      \item Similar features as RAID devices
      \begin{itemize}
         \item Can actually be built on top of RAID
         devices
      \end{itemize}
      \item Better scalability than RAID
      \begin{itemize}
         \item Can easily be resized (up or down)
         \item Can add more devices to grow
      \end{itemize}
   \end{itemize}

\end{frame}

\cprotect\note{


   \textbf{LVM} (\textbf{L}ogical \textbf{V}olume
   \textbf{M}anagement) breaks up one virtual partition into
   multiple chunks each of which can be on different partitions
   and/or disks.

   There are many advantages to using \textbf{LVM}; in
   particular it becomes really easy to change the size of the
   logical partitions and filesystems, to add more storage
   space, rearrange things etc.

   One or more \textbf{physical volumes} (disk partitions) are
   grouped together into a \textbf{volume group}. Then the
   volume group is subdivided into \textbf{logical volumes}
   which mimic to the system nominal physical disk partitions
   and can be formatted to contain mountable filesystems.

   There are a variety of command line utilities tasked to
   create, delete, resize, etc. physical and logical
   volumes. For a graphical tool most \textbf{Linux}
   distributions use \textbf{system-config-lvm}.  However,
   \textbf{RHEL} no longer supports this tool and there is
   currently no graphical tool that works reliably with the
   most recent variations in filesystem types etc. Fortunately, the
   command line utilities are not hard to use and are more
   flexible anyway.

   \textbf{LVM} does impact performance. There is a definite
   additional cost that comes from the overhead of the
   \textbf{LVM} layer. However, even on non-\textbf{RAID}
   systems, if you use \textbf{striping} (splitting of data to
   more than one disk) you can achieve some parallelization improvements.

   Logical volumes have features similar to \textbf{RAID}
   devices (which we will discuss next.) They can actually be built on top of a
   \textbf{RAID} device.  This would give the logical volume
   the redundancy of a \textbf{RAID} device with the scalability of
   \textbf{LVM}.

   \textbf{LVM} has better scalability than \textbf{RAID}: logical
   volumes can easily be resized; i.e., enlarged or shrunk, as
   needs require.  If more space is needed, additional devices
   can be added to the logical volume at any time.
}



