PAS-C01 EBS Bandwidth and IOPS Limits Practice Question
A company runs its SAP ERP system on AWS using a multi-tier architecture. The SAP application servers are in an Auto Scaling group across two Availability Zones, and the SAP HANA database runs on a single large EC2 instance (r5.24xlarge) with 768 GB of memory and EBS Provisioned IOPS SSD (io1) volumes. The operations team recently noticed that the database performance degrades intermittently during peak business hours. CloudWatch metrics show that the database instance's CPU utilization remains below 40%, but the ReadLatency and WriteLatency for the EBS volumes spike above 10 ms during these periods, and the VolumeQueueLength metric increases significantly. The database instance uses a single EBS volume for /hana/data and another for /hana/log. The team has already verified that there are no network bottlenecks and that the SAP application servers are not overwhelming the database with queries. What is the MOST likely cause of the latency spikes, and what action should be taken?
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Upgrade the EC2 instance to a Nitro-based instance type like r5b.24xlarge, which provides higher EBS bandwidth and lower latency.
The symptoms indicate that the EBS volumes are experiencing queueing due to insufficient I/O performance. The r5.24xlarge instance uses the Xen hypervisor, which has lower EBS bandwidth compared to Nitro-based instances like r5b.24xlarge. Upgrading to a Nitro instance provides dedicated EBS bandwidth and lower latency, addressing the latency spikes. Option A is incorrect because st1 (throughput optimized) is not suitable for low-latency database workloads; it is designed for large sequential I/O. Option B is incorrect because adding more application servers would increase the database load, exacerbating the issue. Option C is incorrect because EBS encryption does not improve I/O performance.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Change the EBS volume type from io1 to st1 for higher throughput.
Why it's wrong here
Changing from io1 to st1 is inappropriate because st1 is a throughput-optimized volume designed for large sequential workloads, not for low-latency database operations. It will worsen latency for SAP HANA.
- ✗
Add more SAP application servers to distribute the load and reduce database contention.
Why it's wrong here
Adding more SAP application servers increases the query load on the database, which would exacerbate the EBS queueing and latency issue, not resolve it.
- ✗
Enable EBS encryption on the volumes to improve I/O performance.
Why it's wrong here
Enabling EBS encryption adds a slight overhead for encryption/decryption but does not improve I/O performance or reduce latency. It is unrelated to the observed symptoms.
- ✓
Upgrade the EC2 instance to a Nitro-based instance type like r5b.24xlarge, which provides higher EBS bandwidth and lower latency.
Why this is correct
Upgrading to a Nitro-based instance like r5b.24xlarge provides higher EBS bandwidth and dedicated hardware for EBS, reducing latency and queueing, which directly addresses the issue of EBS volume saturation.
Quick reference
AWS S3 Storage Class Comparison
| Storage Class | Min Duration | Retrieval | Use Case |
|---|---|---|---|
| S3 Standard | None | Immediate | Frequently accessed data |
| S3 Standard-IA | 30 days | Immediate | Infrequent access, rapid retrieval |
| S3 One Zone-IA | 30 days | Immediate | Non-critical infrequent data |
| S3 Intelligent-Tiering | None | Immediate–hours | Unknown or changing access patterns |
| S3 Glacier Instant | 90 days | Milliseconds | Archive with instant retrieval |
| S3 Glacier Flexible | 90 days | Minutes–hours | Archive, flexible retrieval |
| S3 Glacier Deep Archive | 180 days | Hours | Long-term compliance archive |
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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