What are the main Amazon EBS volume types and when do you use each?
gp3 and gp2 are general-purpose SSDs for most workloads. io2 and io1 are provisioned-IOPS SSDs for databases needing high, steady IOPS. st1 is throughput-optimised HDD for big sequential data, and sc1 is cold HDD for rarely used data.
Explain it simply
Choosing an EBS volume is like choosing a vehicle. gp3 is a reliable family car for daily use. io2 is a sports car when speed matters most, like a busy database. st1 is a goods truck, great for hauling large loads in one go. sc1 is a slow cheap tractor for stuff you rarely move.
Example
gp3 (SSD) : default choice, baseline 3000 IOPS and 125 MB/s, IOPS and
throughput can be raised independently of size
gp2 (SSD) : older, IOPS tied to volume size
io2 / io1 : provisioned IOPS SSD, for latency-sensitive databases
st1 (HDD) : throughput optimised, big sequential reads: logs, data warehouse
sc1 (HDD) : cold HDD, lowest cost, infrequent access
Boot volumes: SSD types only (HDD cannot be a boot volume)Pick by the bottleneck. If you need many small random reads and writes, think IOPS and pick SSD. If you stream large files, think MB/s and consider st1.
For most new workloads gp3 is cheaper than gp2 and gives more control, so it is the usual starting point. Move to io2 only when measurements show gp3 cannot meet the IOPS or durability need.
What to say in the interview
"gp3 is my default SSD. For heavy database IOPS I choose io2, for large sequential workloads st1, and for archives sc1. HDD types can't be boot volumes. I choose by whether the workload is IOPS-bound or throughput-bound."
Common mistakes
- Picking io2 by default without measuring need.