CouchDB uses B-trees in an interesting append-only fashion:

http://guide.couchdb.org/draft/btree.html

That makes it work well for reliability and data durability. I have never had it corrupt data over the years. Can always pull the plug on the server (or kill -9 the process) knowing it will recover to a consistent state, or you can also take filesystem snapshot at any time and get a constent database image (I've used that for backups).

Good article. As a side note:

"and you know how high-performing and scalable Perforce servers are"

Sure, their performance is only surpassed by that of the perforce client.

Very interesting and links are gems.