AZ-305 Design data storage solutions Practice Question
A company is designing a storage solution for its backup data. The backups must be stored for 10 years for compliance reasons. The solution should minimize storage costs while ensuring data durability. Which two Azure services should the company consider? (Choose two.)
⚠ Common exam trap
It's easy for candidates to confuse Azure Backup with long-term retention (which is a service that manages backup lifecycle and can use Archive tier) with other Azure storage services that are not designed for cost-effective, long-term archival, such as Azure Files or Azure NetApp Files.
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
✓
Azure Blob Storage Archive tier
Azure Blob Storage Archive tier is correct because it provides the lowest-cost storage for data that is rarely accessed, with a 10-year retention period meeting compliance requirements. It offers 11 nines of durability (99.999999999%) by storing multiple copies across Azure regions, ensuring data integrity over the long term.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Azure Blob Storage Archive tier
Why this is correct
Azure Blob Storage Archive tier is the correct choice because it offers the lowest storage cost per GiB for data that is rarely accessed, such as backups retained for decades. Archive tier supports long-term retention with configurable lifecycle policies, and it provides secure storage with encryption and optional immutability to meet compliance. While data retrieval may require hours of rehydration, for infrequent backup restores this trade-off is acceptable.
- ✗
Azure Files with snapshots
Why it's wrong here
Azure Files with snapshots is not suitable for 10-year backup retention because snapshots are incremental copies stored on the same file share, and their cost accumulates over time based on the size of changed blocks, making long-term retention expensive. Additionally, Azure Files does not offer a native lifecycle policy to migrate snapshots to the Archive tier, and the maximum number of snapshots per share is 200, which is insufficient for a decade of daily backups. Thus, this approach is operationally complex and prohibitively costly.
- ✗
Azure NetApp Files with cross-region replication
Why it's wrong here
Azure NetApp Files with cross-region replication is overkill and extremely costly for an archive workload because Azure NetApp Files provides high-performance enterprise-grade SMB/NFS storage at a premium price per GiB, and cross-region replication compounds that cost by storing duplicate data in a second region. The service also requires provisioning a capacity pool with a minimum throughput level, even if little data is stored, and it lacks a cost-effective archive tier for long-term retention. Consequently, it is impractical for storing backups that are rarely needed over 10 years.
- ✗
Azure Disk Storage with incremental snapshots
Why it's wrong here
Azure Disk Storage with incremental snapshots is intended for capturing point-in-time disk images of VMs, not for storing generic backup archives like database dumps or file data. Disk snapshots are billed on the amount of changed data per snapshot, and because disk storage is priced much higher than Blob Storage—even for the Standard HDD tier—holding 10 years of incremental snapshots would be financially wasteful. There is also no managed archival tier for disk snapshots, so all snapshot data remains in high-cost storage, making this option clearly wrong.
- ✓
Azure Backup with long-term retention policy
Why this is correct
Azure Backup with a long-term retention policy is a valid solution because it is a fully managed backup service that stores recovery points in a Recovery Services vault, which internally uses Azure Blob Storage, including the cost-effective Archive tier for old backups. Its retention policy can keep backups for years or even decades, and it seamlessly integrates with Azure operations via the Backup Center. However, it is a managed orchestration layer, not a raw storage tier, so if the requirement is purely a 'storage solution', Blob Storage Archive tier is the more direct answer.
Quick reference
Azure Blob Storage Tier Comparison
| Tier | Storage Cost | Retrieval Cost | Latency | Use Case |
|---|---|---|---|---|
| Hot | Highest | Lowest | Immediate | Active data, frequent reads |
| Cool | Lower | Higher | Immediate | Data accessed < once / month |
| Cold | Lower still | Higher | Immediate | Data accessed < once / quarter |
| Archive | Lowest | Highest + rehydration delay | Hours | Long-term compliance retention |
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Senior Network & Security Engineer · founder of Courseiva
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