Is it possible to expand out the disk space of an EC2 server once constructed? I would like to put my DB reporting application on an EC2 server but I wanted to make sure I could expand disk space out of a server. I would like to keep my solution as scalable as possible. Thanks!
An EC2 instance can have non-root volumes added and removed as necessary up to the number of volumes available for that instance type. Thusly, the maximum space available to an EC2 instance is the max size of an EBS volume times the number of volumes your instance can have.
The pain here is going to be operational. When you add a new volume, do you migrate the data or restore from a snapshot and grow the file system? How do you manage growth when the present maximum EBS volume size has been filled? In that case, if the application supports it you can move to multiple file systems across an EBS volume each or implement a software-based RAID.
The short answer is "yes, it's possible," but the long answer is, "yes, it's possible but your real constraints are probably operational in nature unless you're dealing with an unusually large amount of data for a DB reporting service."
Your best option may be to use an RDS instance db, increasing space using RDS is extremely easy.