Storage considerations when using Amazon EC2

Amazon Web Services (AWS) provides a variety of instances in their Elastic Compute Cloud (EC2) offerings. With each type of EC2 instance, there are two distinct ways to store data: instance store and Elastic Block Storage (EBS).

Instance store refers to an ephemeral disk that is available as a block device to the instance and is physically present on the host of the instance. By being available on the same host, these disks provide extremely high throughput. However, instance stores are ephemeral and thus provide no guarantees of data retention if an instance is terminated, stopped, or the disk fails. This is clearly not suitable for a single node MongoDB instance, as you might lose your data any time the instance goes down. Not all hope is lost, though. We can use a three or more node replica set and ensure the redundancy of data. For a more robust deployment, we can consider having an extra node in the replica set cluster that uses EBS and has...