When preparing for the AWS Certified Solutions Architect – Associate exam, Amazon EBS volume types often appear. The challenge is not just memorizing names, but understanding what each type is optimized for, and yes, that means having a clear grasp of IOPS vs. Throughput.
EBS Performance Metrics: IOPS and Throughput Explained
When choosing an Amazon EBS volume type, you’ll see two performance terms repeated: IOPS and Throughput. They measure different things, and the exam often tests whether you can tell them apart.
IOPS (Input/Output Operations Per Second)
How many individual read/write requests your storage can handle each second.
Think: speed of handling lots of small, random tasks.
Best for: Databases and transactional systems where predictable, low-latency performance is critical.
Throughput (MB/s)
How much data can flow in/out per second.
Think: the size of the pipe for moving large amounts of data.
Best for: Big data, log processing, and streaming workloads where sequential reads/writes dominate.
Exam tip
“20,000+ IOPS, transactional DB” → correct answer is Provisioned IOPS SSD (io1/io2).
“Streaming, logs, or big data” → correct answer is Throughput-Optimized HDD (st1).
Categories of Amazon EBS Volumes
SSD-Backed Volumes (Fast, Random Access)
gp3 (General Purpose SSD)
Balanced cost and performance.
Up to 16,000 IOPS.
Great for web apps, dev/test, small databases.
io1 / io2 (Provisioned IOPS SSD)
Lets you set exact IOPS (up to 64,000).
Delivers predictable, low-latency performance.
Ideal for mission-critical databases.
HDD-Backed Volumes (Sequential, Large Data)
st1 (Throughput-Optimized HDD):
Focused on throughput (MB/s), not IOPS.
Suited for big data, streaming, and log processing.
Lower cost than SSDs.
sc1 (Cold HDD):
Lowest cost, lowest performance.
Best for archival data or infrequent access.
Quick Reference Table
Volume Type | Max IOPS | Optimized For | Best Use Case |
|---|---|---|---|
gp3 (SSD) | 16,000 | Balanced price/performance | Most workloads, dev/test |
io1/io2 (SSD) | 64,000 | High IOPS, predictable latency | Mission-critical databases |
st1 (HDD) | ~500 | High throughput | Logs, big data, streaming |
sc1 (HDD) | ~250 | Lowest cost storage | Archival, infrequent access |
Exam Takeaways
Yes — IOPS knowledge is needed.
Many questions include clues like “transactional DB with 20,000 IOPS” → correct answer is io1/io2.Throughput vs. IOPS is the key distinction.
IOPS-heavy → SSD (gp3, io1/io2)
Throughput-heavy → st1
Archival → sc1
gp3 is the common distractor.
Great for most workloads, but cannot exceed 16,000 IOPS.
By mastering EBS volume families and knowing when IOPS vs throughput matters, you can eliminate wrong answers and confidently select the right one under exam pressure.
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