Testing a distributed system can be trying even under the best of circumstances.
Distributed systems can be especially difficult to program, for a variety of reasons. They can be difficult to design, difficult to manage, and, above all, difficult to test. Testing a normal system can be trying even under the best of circumstances, and no matter how diligent the tester is, bugs can still get through. Now take all of the standard issues and multiply them by multiple processes written in multiple languages running on multiple boxes that could potentially all be on different operating systems, and there is potential for a real disaster.
Rethinking the Fundamental Abstractions of the File System
The reading and writing of data, one of the most fundamental aspects of any Von Neumann computer, is surprisingly subtle and full of nuance. For example, consider access to a shared memory in a system with multiple processors. While a simple and intuitive approach known as strong consistency is easiest for programmers to understand, many weaker models are in widespread use (e.g., x86 total store ordering); such approaches improve system performance, but at the cost of making reasoning about system behavior more complex and error-prone. Fortunately, a great deal of time and effort has gone into thinking about such memory models, and, as a result, most multiprocessor applications are not caught unaware.