The Jeff’s Note (Contextual Hook) #
Jeff’s Note #
Unlike generic exam dumps, ADH analyzes this scenario through the lens of a Real-World Site Reliability Engineer.
For SOA-C02 candidates, the confusion often lies in distinguishing the different Storage Gateway volume types and their local data availability guarantees. In production, this is about understanding exactly when data is persisted locally versus in the cloud, and how POSIX compatibility influences gateway selection. Let’s drill down.
The Certification Drill (Simulated Question) #
Scenario #
BlueBox Logistics operates a critical on-premises application that stores sensitive routing data. They want to set up a backup system leveraging AWS, but with strict requirements: all backup data must remain locally accessible on-premises. Additionally, their legacy backup software only supports writing to block-based storage that conforms to POSIX standards.
The Requirement: #
Identify the AWS backup solution that enables local, POSIX-compliant block storage accessible by the backup software, while integrating with AWS for offsite durability.
The Options #
- A) Configure the backup software to use Amazon S3 as the target for the data backups.
- B) Configure the backup software to use Amazon S3 Glacier as the target for the data backups.
- C) Use AWS Storage Gateway, and configure it to use gateway-cached volumes.
- D) Use AWS Storage Gateway, and configure it to use gateway-stored volumes.
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Correct Answer #
D) Use AWS Storage Gateway, and configure it to use gateway-stored volumes.
Quick Insight: The SysOps Imperative #
Among Storage Gateway volume options, gateway-stored volumes ensure full data availability locally on-premises, suitable for applications requiring POSIX-compliant block storage. This contrasts with gateway-cached volumes, which keep only frequently accessed data locally, with primary storage in AWS.
Content Locked: The Expert Analysis #
You’ve identified the answer. But do you know the implementation details that separate a Junior from a Senior?
The Expert’s Analysis #
Correct Answer #
Option D
The Winning Logic #
- Gateway-stored volumes store the entire dataset locally on-premises, providing full, low-latency access using iSCSI block storage interfaces that comply with POSIX standards.
- This satisfies the legacy backup application’s requirement to write directly to a block-based POSIX file system.
- Data is asynchronously backed up to AWS, providing durability offsite without compromising local availability.
- Gateway-cached volumes (Option C) keep only a cache locally while writing primary data in AWS, which would break the requirement for all data to be available locally.
- Amazon S3 (Option A) and S3 Glacier (Option B) provide object storage with different access models, incompatible with POSIX block storage and local on-premises access requirements.
The Trap (Distractor Analysis): #
- Why not A? Amazon S3 is object storage, accessed over HTTPS REST APIs, incompatible with the legacy backup application’s POSIX block-based writes.
- Why not B? S3 Glacier is archival storage with high retrieval latency, unsuitable as a live backup target.
- Why not C? Gateway-cached volumes only cache data locally; primary data lives in AWS, so local availability of all backup data is not guaranteed.
The Technical Blueprint #
# To create a gateway-stored volume via AWS CLI:
aws storagegateway create-stored-iscsi-volume \
--gateway-arn arn:aws:storagegateway:region:account-id:gateway/gateway-id \
--disk-id disk-id \
--network-interface-id eni-id \
--client-token unique-token
This command provisions a stored volume that keeps all data locally with asynchronous backups to AWS.
The Comparative Analysis #
| Option | Operational Overhead | Automation Level | Impact on Local Availability |
|---|---|---|---|
| A | Low (S3 is managed) | High | No local block storage, incompatible |
| B | Low but retrieval delayed | High | No local access, data archived offsite |
| C | Moderate (cache management) | Moderate | Partial local data only, violates full local requirement |
| D | Higher - gateway hardware | Moderate | Full local data availability (meets POSIX block storage need) |
Real-World Application (Practitioner Insight) #
Exam Rule #
For the exam, always pick Storage Gateway with gateway-stored volumes when you see a backup solution requiring full local block storage with POSIX compatibility.
Real World #
In production, many companies use gateway-cached volumes for cost efficiency, since they reduce on-premises hardware storage needs, but this is unsuitable where local availability is mandatory or legacy applications require block storage.
(CTA) Stop Guessing, Start Mastering #
Disclaimer
This is a study note based on simulated scenarios for the SOA-C02 exam.