Exams / SAA-C03 / Block storage cost / Question 1
SAA-C03 practice question: Block storage cost
Design Cost-Optimized Architectures A free question from our original SAA-C03 practice exam. Try it, then open the answer to see why each option is right or wrong.
A company has 300 Amazon EBS gp2 volumes of 500 GiB each, attached to running EC2 instances. Monitoring shows that each volume peaks at about 2,500 IOPS and 110 MiB/s. During long busy periods, some volumes run out of burst credits and slow down. The company wants lower storage costs and steady performance, and the instances must stay online. Which solution meets these requirements MOST cost-effectively?
Choose one answer.
- AA. Use Elastic Volumes to grow each gp2 volume to 1,000 GiB, giving a 3,000 IOPS baseline that does not depend on burst credits.
- BB. Use Elastic Volumes to change each volume to io2 with 3,000 provisioned IOPS, keeping the 500 GiB size.
- CC. Use Elastic Volumes to change each volume to gp3 with 3,000 IOPS and 125 MiB/s, keeping the 500 GiB size.
- DD. Snapshot each volume, create gp3 volumes from the snapshots, and swap them onto the instances during a maintenance window.
Show the answer and explanation
Answer: C
- A. Wrong: gp2 gives 3 IOPS per GiB, so 1,000 GiB does provide a steady 3,000 IOPS baseline, and Elastic Volumes can grow volumes while they are in use. But doubling the storage roughly doubles the bill, which works against the goal of lowering cost. Learn more: Amazon EBS General Purpose SSD volumes (opens in a new tab)
- B. Wrong: io2 Provisioned IOPS volumes give steady performance, but they are built for demanding I/O workloads and bill for every provisioned IOPS on top of storage. gp3 includes 3,000 IOPS in its storage price, so io2 would raise costs for no benefit here. Learn more: Amazon EBS pricing (opens in a new tab)
- C. Right: Correct. A 500 GiB gp2 volume has a baseline of only 1,500 IOPS and relies on burst credits to reach 3,000. gp3 includes a steady 3,000 IOPS and 125 MiB/s, which covers the 2,500 IOPS and 110 MiB/s peaks, costs about 20% less per GiB, and Elastic Volumes changes the type while the volume stays in use. Learn more: Modify an Amazon EBS volume using Elastic Volumes operations (opens in a new tab)
- D. Wrong: gp3 is the right volume type, but detaching and swapping volumes means taking applications offline, which the company has ruled out. Elastic Volumes can change the type of an attached volume in place, so there is no need for snapshots and a maintenance window. Learn more: Modify an Amazon EBS volume using Elastic Volumes operations (opens in a new tab)
Explanation
gp2 performance scales at 3 IOPS per GiB, so a 500 GiB volume has a 1,500 IOPS baseline and only reaches 3,000 IOPS while burst credits last. gp3 includes 3,000 IOPS and 125 MiB/s regardless of size, never relies on burst credits, and has a 20% lower price per GiB than gp2. Elastic Volumes changes the type of an attached volume while it is in use, so the instances stay online.
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