DEA-C01 Data Store Management Practice Question
A company uses Amazon EMR to process large datasets stored in Amazon S3. The cluster uses a transient configuration and stores intermediate data on HDFS. After a job fails due to a spot instance termination, the data engineer needs to rerun the job. What should the engineer do to minimize data loss and cost?
⚠ Common exam trap
Candidates often assume storing intermediate data in S3 (EMRFS) is always better for durability, but they overlook that HDFS replication with spot/on-demand mix provides a cheaper, faster recovery for transient cluster workloads without incurring S3 write costs.
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
✓
Configure the cluster with a mix of spot and on-demand instances and set HDFS replication to 3.
Using a mix of spot and on-demand instances balances cost savings with fault tolerance, while setting HDFS replication to 3 ensures that intermediate data on HDFS survives the loss of a single node (e.g., a terminated spot instance). This allows the job to resume from the last checkpoint or reduce recomputation, minimizing both data loss and cost.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Use a long-running cluster with all on-demand instances to avoid interruptions.
Why it's wrong here
This increases cost significantly and does not address spot interruptions.
- ✓
Configure the cluster with a mix of spot and on-demand instances and set HDFS replication to 3.
Why this is correct
This balances cost and reliability; on-demand instances provide stability for HDFS NameNode and critical nodes.
- ✗
Configure the cluster to use EMRFS and store intermediate data in S3.
Why it's wrong here
EMRFS is for persistent data, not intermediate data; writing intermediate data to S3 is slower and more expensive.
- ✗
Increase the HDFS replication factor to 5 and use only spot instances.
Why it's wrong here
Higher replication factor increases storage cost, and using only spot instances risks losing the entire cluster.
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 |
Go deeper
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This DEA-C01 practice question is part of Courseiva's free Amazon Web Services certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the DEA-C01 exam.