Added an introduction. Brushed up the chapter on varnish in a virtualized environment

doc/sphinx/tutorial/index.rst

@@ -14,6 +14,7 @@ separate topic. Good luck.
 
 .. toctree:: :maxdepth: 1
 
+        indroduction
 	backend_servers
         starting_varnish
 	logging

doc/sphinx/tutorial/introduction.rst

+.. _tutorial-intro:
+
+What is Varnish?
+----------------
+
+Varnish Cache is a Varnish Cache is a web application accelerator also
+known as a caching HTTP reverse proxy. You install it in front of any
+server that speaks HTTP and configure it to cache the
+contents. Varnish Cache is really, really fast. It typically speeds up
+delivery with a factor of 300 - 1000x, depending on your architecture.
+
+
+Performance
+~~~~~~~~~~~
+
+Varnish performs really, really well. It is usually bound by the speed
+of the network, effectivly turning performance into a non-issue. We've
+seen Varnish delivering 20 Gbps on regular off-the-shelf hardware.
+
+Flexibility
+~~~~~~~~~~~
+
+One of the key features of Varnish Cache, in addition to it's
+performance, is the flexibility of it's configuration language,
+VCL. VCL enables you to write policies on how incoming requests should
+be handled. In such a policy you can decide what content you want to
+serve, from where you want to get the content and how the request or
+response should be altered. You can read more about this in our
+tutorial.
+
+
+Supported plattforms
+~~~~~~~~~~~~~~~~~~~~
+
+Varnish is written to run on modern versions of Linux and FreeBSD and
+the best experience is had on those plattforms. Thanks to our
+contributors it also runs on NetBSD, OpenBSD and OS X.

doc/sphinx/tutorial/virtualised.rst

 
-Running inside a virtual machine (VM)
--------------------------------------
+Running Varnish in a virtualized environment
+--------------------------------------------
 
-It is possible, but not recommended for high performance, to run Varnish on virtualised 
-hardware.
+It is possible, but not recommended for high performance, to run
+Varnish on virtualised hardware. Reduced disk- and network performance
+will reduce the performance a bit so make sure your system has good IO
+performance.
 
 OpenVZ
-''''''
+~~~~~~
 
-If you are running on 64bit OpenVZ (or Parallels VPS), you must reduce the 
-maximum stack size before starting Varnish. The default allocates to much memory per thread, 
-which will make varnish fail as soon as the number of threads (==traffic) increases.
+If you are running on 64bit OpenVZ (or Parallels VPS), you must reduce
+the maximum stack size before starting Varnish. The default allocates
+to much memory per thread, which will make varnish fail as soon as the
+number of threads (==traffic) increases.
 
 Reduce the maximum stack size by running::