6.4. StormCellar Overview

The primary goal of StormCellar is to leverage substantially cheaper disk to accommodate the demands of today's news volume. To do this, StormCellar takes advantage of the average reader's (based of field trials at three large commercial sites) tendency to hit the first 40 or so hours of posts at a rate that is 70% greater than all other days combined.

As you may already know, Tornado aggregates content from multiple Tornado Back End servers. A StormCellar looks and acts like just like another back end server to the Tornado Front Ends and is handled normally, but in fact something very different is going on behind the scenes.

StormCellar content picks up its retention where the primary backends leave off. For example, a given StormCellar may have 4 Terabytes of disk, representing 5 days of retention, but starting 6 days in the past; it will only be called upon for posts that are between 6 and 11 days old. Newer posts are retrieved from faster storage separate from StormCellar.