Commit 2bcd2f0f authored by Per Buer's avatar Per Buer

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

parent 6bec2c83
......@@ -14,6 +14,7 @@ separate topic. Good luck.
.. toctree:: :maxdepth: 1
indroduction
backend_servers
starting_varnish
logging
......
.. _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.
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::
......
Markdown is supported
0% or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment