Migrate EBS gp2 volumes to gp3 and cut storage cost by about 20%

Short version: AWS gp3 EBS volumes cost about ~20% less per GB than gp2 ($0.08 vs $0.10 per GB-month in us-east-1) and includes 3,000 IOPS and 125 MB/s of baseline performance for free. You can convert a volume from gp2 to gp3 online, with no downtime and no snapshot with a single modify-volume call. For most volumes, it's a real savings. Here's how to find those volumes, migrate them, and the one caveat to keep in mind.

Why gp3 is cheaper (and usually faster)

gp2 pricing couples performance to its size: you get 3 IOPS per GB, so the only way to get more IOPS on gp2 is to over-provision storage you don't need. gp3 removes that coupling:

gp2

gp3