DEA-C01 Data Store Management Practice Question
A company is migrating an on-premises Apache Hadoop cluster to Amazon EMR. The data is stored in HDFS and must be moved to Amazon S3. Which THREE considerations are important when designing the migration? (Choose THREE.)
⚠ Common exam trap
Test-takers frequently assume S3 supports POSIX semantics or that HDFS can be directly mounted as an S3 bucket, confusing the object storage model with a traditional filesystem, leading them to select options A or B.
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
✓
EMR can read data directly from S3 using EMRFS
Amazon EMR uses the EMR File System (EMRFS) to directly read and write data stored in Amazon S3, treating S3 as a scalable, durable data lake without needing to first copy data into HDFS. This allows EMR clusters to process data directly from S3, enabling decoupled compute and storage.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
S3 supports POSIX file system semantics
Why it's wrong here
S3 is an object store, not POSIX-compliant.
- ✗
HDFS can be directly mounted as an S3 bucket
Why it's wrong here
HDFS and S3 are different filesystems; can't mount directly.
- ✓
EMR can read data directly from S3 using EMRFS
Why this is correct
EMRFS allows EMR to access S3 as a filesystem.
- ✓
S3 provides eventual consistency for overwrite PUTS and DELETES
Why this is correct
This is a key difference from HDFS's strong consistency.
- ✓
Using S3 as the data store allows independent scaling of compute and storage
Why this is correct
S3 decouples storage from compute, offering elasticity.
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
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