SOA-C02 Practice Question 10: GP2 to GP3 Cost Optimization
AWS Certified SysOps Administrator – Associate (SOA-C02) · Test 1 · question 10 of 10
A company runs 200 EC2 instances, each with a 500 GiB General Purpose SSD (gp2) data volume. CloudWatch shows that the volumes never exceed 1,200 IOPS or 90 MiB/s of throughput. Management asks for lower EBS spend, and the applications cannot tolerate downtime during the change.
Which action reduces cost while preserving current performance?
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Answer:
gp3 costs about 20 percent less per GiB than gp2 and includes a baseline of 3,000 IOPS and 125 MiB/s at no extra charge, independent of volume size. That baseline comfortably covers the observed 1,200 IOPS and 90 MiB/s, and unlike gp2 it is sustained rather than credit-based. An Elastic Volumes modification changes the volume type in place while the instance stays running, so there is no downtime.
Option A is wrong on performance. st1 volumes are HDD-backed, optimised for large sequential throughput, and are not supported as boot volumes; their IOPS characteristics would badly hurt the random I/O these volumes are serving.
Option C reduces the bill only by shrinking capacity the application presumably needs, requires a restore and a filesystem change, and cannot be done in place; EBS volumes can be grown but not shrunk with Elastic Volumes.
Option D increases cost. io2 has a higher per-GiB price than gp3 and charges separately for every provisioned IOPS, whereas gp3's first 3,000 IOPS are free. io2 is justified by sub-millisecond consistency or higher durability requirements, neither of which the stem mentions.
Reference: Amazon EBS General Purpose SSD volumes