When you attach an EBS volume to an EC2 instance, you’ll see a prompt like this if you’re using the console:
What if you have already used /dev/sdf to /dev/sdp1? You can still use other names!
Here is the AWS documentation for device naming. I’ve copied the relevant table below.
/dev/sd[f-p] are recommended, but you can use the rest of the letters (except for whatever is reserved for root).