A team runs a mission-critical database and wants to maximize the underlying EBS volume's durability without switching to an entirely different storage architecture. They are choosing between io1 and io2 Provisioned IOPS SSD volumes. Which option is correct?
- io2, because it is designed for 99.999% annual durability, versus io1's 99.8%-99.9%, while offering the same Provisioned IOPS SSD architecture
- io1, because it supports a higher maximum IOPS ceiling than io2 in every AWS Region
- gp3, because General Purpose SSD volumes now match Provisioned IOPS SSD durability at a lower cost
- st1, because Throughput Optimized HDD volumes are rated for the same 99.999% durability as io2 at a fraction of the price
Why A? And why not the others?
Correct answer: A. io2, because it is designed for 99.999% annual durability, versus io1's 99.8%-99.9%, while offering the same Provisioned IOPS SSD architecture
io2 volumes are designed for 99.999% durability (an annual failure rate of about 0.001%), a full order of magnitude better than io1's 99.8%-99.9% durability (0.1%-0.2% annual failure rate), while both remain the same Provisioned IOPS SSD category built for sustained, low-latency, high-IOPS workloads like mission-critical databases, so io2 is the volume type suited to maximizing durability without changing architecture. The option favoring io1 for its IOPS ceiling gets the comparison backwards: io2 supports a higher maximum IOPS ceiling than io1 where it's available, not the reverse, and IOPS ceiling isn't the durability question being asked anyway. The option claiming gp3 now matches Provisioned IOPS SSD durability is incorrect: gp3, like gp2, remains rated at 99.8%-99.9% durability, the same tier as io1, not io2's 99.999%. The option proposing st1 is wrong on two counts: Throughput Optimized HDD is rated at 99.8%-99.9% durability, not 99.999%, and it is designed for large sequential throughput workloads such as big data and log processing, not low-latency transactional database access.
Source: AWS EBS documentation: Amazon EBS volume types — durability comparison (io2 vs io1)