[eva2000]

no demos but if you google for 'Digital Point modules: Sphinx-based search' the copyright from shawn's sphinx search link you will find vB forums using the plugin and get an idea of how fast search is

it's very fast ! alot of my private clients i setup vb4 digitalpoint sphinx search for and it's blistering fast for forums with up to 60 million posts from my own experience !

it isn't built inside specifically, search and search data are handled by sphinx search which you need to install from sphinxsearch.com on your server (hence why it isn't possible by default out of box - it's server software dependent on you installing and configuring properly sphinx search - just like vB is dependent on working apache, php and mysql setup) and search index data is usually on disk separately, default to /home/sphinx-data if you follow shawn's instructions but can be on any disk partition

edit: just quoting myself

To give you an idea, I installed this vB4 plugin and Sphinx search http://sphinxsearch.com/about/sphinx/ on a 5.5 million post forum. The difference and load compared to default vB4 search is like night and day.

Before
- vB4 default search took around 57-60 seconds to return a common keyword search term of their forums which locks on MySQL tables affecting all other vB members usage of the forums.

After
- Sphinx search + vB4 sphinx plugin installed to replace vB4 default search, the same search term only took 0.18 to 0.30 seconds to return - that's 333x times faster! And without any negative effect for other vB members' experience on the forums.

Also reindexing search (needed create proper indexes for search terms - without this indexing your vB search feature will not return any results), for

- vB4 default search on 5.5 million post forum took around 3-5 days to reindex. Note while reindexing, majority of search keyword terms will not return any results until the keyword term is added to the indexing. So for 3-5 days search will be essentially broken to members not able to search for keyword terms.
- With Sphinx search plugin, it only takes around 10-15 minutes - that's 720x times faster!