When creating an EC2 instance, AWS gives a choice to create a primary and secondary volume. The secondary volume is suggested to be much bigger than the primary, usually. So what kind of data is stored in which volume. Can I control which volume to be used when running programs/downloading/storing data? What are the differences between using just one single big volume instead of two volumes this way?

CodePudding user response：

The only real difference is that the primary volume has the operating system installed on it. That means you have to consider a few things:

• It can be more difficult to increase the size of the primary volume later.
• You can't detach and reattach the primary volume while the server is running.

You could think of a primary volume like the hard drive installed inside your laptop. It has your operating system on it, and it can be a fairly involved process to change it out. Then you would think of secondary volumes like external USB hard drives that you could add and remove from your computer whenever you want without any issues, and you can upgrade it very easily.

Can I control which volume to be used when running programs/downloading/storing data?

It is exactly like plugging multiple hard drives into your laptop. You will have different filesystem paths on your EC2 server that correspond to the different volumes that are mounted on the server.

What are the differences between using just one single big volume instead of two volumes this way?

It's generally easier to grow the size of secondary volumes, and to move them around between different servers.