How CouchDB Treats the Disks

Blogs are pretty much append-only. Most of the time you add new posts, sometimes you edit recent ones. There are new comments.

CouchDB's file format is also append-only. This doesn't make it special, lots of databases have used similar techniques before, but it does make it more like web data.

It also makes it smooth for the disk, because the disk doesn't have to seek for writes, and most reads are from file-system cache.

Here's some slides:

Intro to CouchDB's Append Only B-Tree (9MB pdf) Feel free to reuse with attribution.