We started the day with James Cowling from Dropbox talking about how the company’s exabyte-scale system protects all of its documents. Instead of describing the system architecture, which he wrote about in a blog post, he talked about what it takes to preserve data in the face of all kinds of faults — including system components, processes, and human error. He drove home the point that basic data redundancy techniques are just a starting point; meaningful reliability at scale comes from simplicity of design and relentless verification. He also shared a fascinating story of how the team moved 2 EB of data from S3 into their new store over a short period of time. The insights shared in this talk are widely applicable to a variety of high-scale systems that have high availability constraints.