Backblaze needs petabytes of storage, but Amazon S3, EMC, NetApp, etc. were outrageously expensive - so we built our own, in a lean-startup way. We show how this went from a wood prototype to 15 petabytes of cloud storage. We open-sourced the design and 500,000 read the blog post and hundreds of companies are now using these storage pods.
The original blog post: http://blog.backblaze.com/2009/09/01/petabytes-on-a-budget-how-to-build-cheap-cloud-storage/