Magento2 Cache – Built-in Cache vs. Varnish Cache for Full Page Cache

We have used Lightspeed (http://www.tinybrick.com/improve-magentos-slow-performance.html) in quite a few projects and also consider using Zoom Full Page Cache as it seems a free viable option. The speed improvement is very good, all full page cache modules work by caching the whole html page (usually for cms pages, products and categories). Even if the cache is based on files the speed boost is visible. The only case where I would not consider these modules is if you are having most of your traffic coming from logged in users, as most of the community cache modules will not cache much. If this is the case, the best option is the built-in Full Page Cache on Magento Enterprise.

It can depend on how your site/server was setup. That being said, in my app/etc/local.xml of a EE 1.13 site, using the built in Redis, I have the following:

<full_page_cache>
<backend>Mage_Cache_Backend_Redis</backend>
<backend_options>
    <server>127.0.0.1</server> <!-- or absolute path to unix socket -->
<port>6380</port>
<persistent></persistent> <!-- Specify a unique string like "cache-db0" to enable persistent connections. -->
<database>1</database> <!-- Separate database 1 to keep FPC separately -->
<password></password>
<force_standalone>0</force_standalone>  <!-- 0 for phpredis, 1 for standalone PHP -->
<connect_retries>1</connect_retries>    <!-- Reduces errors due to random connection failures -->
<lifetimelimit>57600</lifetimelimit>    <!-- 16 hours of lifetime for cache record -->
<compress_data>0</compress_data>        <!-- DISABLE compression for EE FPC since it already uses compression -->
</backend_options>
</full_page_cache>

Realistically, more information will need to be known because it will depend on what kind of server you have, who your host is (and whether it is a dedicated or shared box), what caching strategies are available on the server, etc.