When Amazon Web Services EC2 launched in 2006, it looked a lot different than we know it today. One of the primary differences was how AWS handled virtual machine storage. At that time, AWS only offered ephemeral storage for virtual machine instances. Consider a user booting an EC2 instance with an instance type (or flavor) that offered a 20 GB primary disk and a 50 GB secondary disk. Any data written to those local disks (that is, /dev/xvda or /dev/xvdb inside the operating system) would reside on the compute node hosting that instance. See Figure 7.1.
Figure 7.1: Amazon EC2 virtual machine ephemeral storage
It wasn't long before many users encountered problems:
- Data copied to the disks could not be easily transferred to other virtual machines.
- Stopping or terminating the instance meant complete data loss (once started again, the virtual machine would boot...
