[FE training-materials-updates] Reintroduce the FTL slide in the block-filesystems section

[Boris Brezillon]

Repository : git://git.free-electrons.com/training-materials.git

On branch  : mtd-rework-WIP
Link       : http://git.free-electrons.com/training-materials/commit/?id=fb5d3f6e1261764df30c337b93f138718b1b6ad0

>---------------------------------------------------------------

commit fb5d3f6e1261764df30c337b93f138718b1b6ad0
Author: Boris Brezillon <boris.brezillon at free-electrons.com>
Date:   Wed May 27 09:09:20 2015 +0200

    Reintroduce the FTL slide in the block-filesystems section
    
    Signed-off-by: Boris Brezillon <boris.brezillon at free-electrons.com>


>---------------------------------------------------------------

fb5d3f6e1261764df30c337b93f138718b1b6ad0
 .../sysdev-block-filesystems.tex                       | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/slides/sysdev-block-filesystems/sysdev-block-filesystems.tex b/slides/sysdev-block-filesystems/sysdev-block-filesystems.tex
index fdc382d..e0464f5 100644
--- a/slides/sysdev-block-filesystems/sysdev-block-filesystems.tex
+++ b/slides/sysdev-block-filesystems/sysdev-block-filesystems.tex
@@ -248,6 +248,24 @@ major minor #blocks name
   \end{columns}
 \end{frame}
 
+\begin{frame}
+  \frametitle{Issues with flash-based block storage}
+  \begin{itemize}
+  \item Flash storage made available only through a block interface.
+  \item Hence, no way to access a low level flash interface
+    and use the Linux filesystems doing wear leveling.
+  \item No details about the layer (Flash Translation Layer) they
+    use. Details are kept as trade secrets, and may hide poor
+    implementations.
+  \item Can use {\em flashbench}
+        (\url{https://github.com/bradfa/flashbench}) to find out
+        the erase block size and optimize filesystem formating.
+  \item Not knowing about the wear leveling algorithm,
+        it is highly recommended to limit the number of writes
+        to these devices.
+  \end{itemize}
+\end{frame}
+
 \setuplabframe
 {Block filesystems}
 {