AZ-305 Availability set Practice Question
A company runs a SQL Server database on an Azure virtual machine in a single region. They need to increase storage capacity and improve I/O performance for their transaction-intensive workload. They also want to ensure high availability within the same datacenter (99.99% SLA). What should they do?
⚠ Common exam trap
Candidates often think that simply using high-performance disks (like Premium SSD v2 or Ultra Disk) is sufficient for the SLA. However, the 99.99% SLA requires multiple VMs in an availability set. Storage Spaces Direct with availability set provides both performance and HA within a datacenter.
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
✓
Deploy the SQL Server on an availability set and use Storage Spaces Direct with multiple disks.
To achieve 99.99% availability within a single datacenter, you need multiple VMs in an availability set. Option C combines an availability set with Storage Spaces Direct (S2D), which uses multiple disks across VMs to provide both performance (through disk pooling) and high availability (via mirroring). This meets all requirements: increased storage capacity, improved I/O performance, and 99.99% SLA. Option A only addresses disk performance and redundancy but fails to provide VM-level redundancy, which is necessary for the SLA.
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 Azure Premium SSD v2 managed disks in a storage pool with mirroring across multiple disks.
Why it's wrong here
While Azure Premium SSD v2 disks offer high performance, attaching them to a single VM (even with a storage pool) does not provide the required 99.99% SLA because a single VM failure would cause downtime. No multiple VMs or availability set is mentioned.
- ✗
Use Azure Ultra Disk storage attached to the VM.
Why it's wrong here
Azure Ultra Disk provides high performance but is attached to a single VM, so it does not address high availability. Also, it cannot be pooled for capacity aggregation as effectively as Premium SSD v2 with storage pools.
- ✓
Deploy the SQL Server on an availability set and use Storage Spaces Direct with multiple disks.
Why this is correct
Correct. Deploying SQL Server on an availability set ensures multiple VMs are in separate fault domains and update domains, achieving 99.99% SLA. Storage Spaces Direct pools multiple disks across VMs, providing both increased capacity and I/O performance through mirroring, while also offering data redundancy.
- ✗
Enable Azure SQL Managed Instance with auto-failover groups.
Why it's wrong here
Azure SQL Managed Instance with auto-failover groups is a PaaS solution that provides high availability across regions, not within a single datacenter. The question specifically requires within the same datacenter, and the workload is on IaaS, so this option is not appropriate.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This AZ-305 practice question is part of Courseiva's free Microsoft 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 AZ-305 exam.