SAP-C02 Practice Question 36: Shared Block Storage Performance
AWS Certified Solutions Architect – Professional (SAP-C02) · Test 4 · question 6 of 10
A trading firm runs a self-managed PostgreSQL database on Nitro-based EC2 instances. Two changes are being made at once. The workload has grown and now needs a sustained 120,000 IOPS on the data volume with consistently sub-millisecond latency, rather than the bursty profile it has today on a single gp3 volume. At the same time, the team is adopting a clustered failover product that requires the same block volume to be attached to two EC2 instances in the same Availability Zone simultaneously, so that the passive node can take over without a detach-and-reattach step.
The risk register also calls for the highest volume durability AWS offers for block storage. Which storage configuration meets all three requirements?
Show answer and explanation
Answer:
Only Provisioned IOPS SSD satisfies all three constraints at once. io2 Block Express supports up to 256,000 IOPS and 4,000 MiB/s on Nitro-based instances, is designed for an average latency under 500 microseconds, is the only EBS volume type rated at 99.999% durability, and is the volume family that supports Amazon EBS Multi-Attach, attaching one volume to multiple instances in the same Availability Zone. That last point is the discriminator: it is the requirement that eliminates every other option.
Option A can reach the IOPS number by striping, since each gp3 volume tops out at 80,000 IOPS and 2,000 MiB/s, but General Purpose SSD volumes do not support Multi-Attach, so the clustered failover product cannot work. RAID 0 also multiplies the failure domain and leaves durability at the 99.8%–99.9% of gp3.
Option B fails on two counts. An io1 volume maxes out at 64,000 IOPS, about half of what is required, and although io1 supports Multi-Attach it carries the same 99.8%–99.9% durability as gp3 rather than the highest AWS offers.
Option D delivers very high IOPS but instance store is ephemeral local storage tied to one instance. It cannot be attached to a second instance at all, and its contents are lost when the instance stops or fails, the opposite of the durability requirement.
Reference: Amazon EBS volume types