MLS-C01 Modeling Practice Question
Exhibit
Refer to the exhibit. ``` Training job status: Failed Error: ClientError: Data download failed. The downloaded file size (0 bytes) does not match expected size (1024 bytes). Check that the S3 object exists and is readable. ```
A data scientist runs a SageMaker training job that fails with the above error. The S3 bucket and object exist, and the IAM role has s3:GetObject permission. What is the MOST likely cause?
⚠ Common exam trap
Watch out — candidates often assume permission or network issues are the root cause, but the error specifically points to a data integrity problem, which is a subtle but critical detail in SageMaker's S3 interaction.
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
✓
The S3 object was uploaded with incorrect checksum or is corrupted
The error indicates that SageMaker cannot read the S3 object, even though the bucket and object exist and the IAM role has s3:GetObject permission. The most likely cause is that the object was uploaded with an incorrect checksum or is corrupted, which prevents SageMaker from verifying the integrity of the data during the training job initialization. SageMaker uses ETag (MD5 checksum) validation when reading objects, and a mismatch triggers a failure.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
The S3 object was uploaded with incorrect checksum or is corrupted
Why this is correct
A corrupted file can cause size mismatch and zero-byte download.
- ✗
The training instance does not have internet access
Why it's wrong here
SageMaker uses VPC endpoints or internet; lack of internet would cause timeout, not size mismatch.
- ✗
The S3 bucket has versioning enabled and the object version is not specified
Why it's wrong here
If versioning is enabled, SageMaker uses latest version unless specified; would not cause zero bytes.
- ✗
The IAM role lacks kms:Decrypt permission for an encrypted S3 object
Why it's wrong here
Missing KMS permission would cause access denied, not size mismatch.
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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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This MLS-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 MLS-C01 exam.