Difference between the Amazon Linux 2 AMI

I launched both and they appear to be identical. One says ebs and the other is gp2.

ami-b270a8cf amzn2-ami-hvm-2017.12.0.20180328.1-x86_64-ebs
ami-f973ab84 amzn2-ami-hvm-2017.12.0.20180328.1-x86_64-gp2

The difference in that ami-b270a8cf ebs uses magnetic storage for the root volume and ami-f973ab84 gp2 uses General Purpose (SSD) storage for the root volume.

AWS's lack of documentation explaining the actual difference between the two (if there is I'll gladly edit this answer) is a bit surprising so I'm adding my own take to this

TLDR;

If you're planning on switching to a faster SSD root volume at some point in the future but want to use Magnetic for now it would be better to use the gp2 version of the AMI and then change the root volume to SSD sometime later

Some more Explanation

• ami-f973ab84 amzn2-ami-hvm-2017.12.0.20180328.1-x86_64-gp2 - The recommended root volume type is General Purpose SSD (gp2)
• ami-b270a8cf amzn2-ami-hvm-2017.12.0.20180328.1-x86_64-ebs - The recommended root volume type is Magnetic

However this isn't set in stone so you can still interchange between them (I've used the gp2 version with a Magnetic storage in the past without issues)

I couldn't find any official documentation as to the actual difference between the two AMI versions but the gp2 version most likely has SSD related optimizations added already to the OS

So if you envision switching to SSD at some point in future but want to start with a Magnetic volume it might be better to just use the gp2 optimized AMI right from the start. It probably has some optimizations not relevant to Magnetic volumes but it might be more future proof in case you want to have a faster root volume later