Disk Storage in Azure
Azure Disk Storage provides persistent storage for Virtual Machines. Every VM in Azure needs at least one disk — the OS Disk. You can add more disks (Data Disks) depending on your workload.
Types of Managed Disks
- Premium SSD: High performance, low latency (ideal for production databases or I/O-intensive apps).
- Standard SSD: Balanced performance and cost (general workloads, dev/test).
- Standard HDD: Lowest cost, higher latency (good for backups or infrequent access).
- Ultra Disk: Extreme performance with adjustable throughput (only for very high-end workloads).
Disk Categories
- OS Disk: Boots the VM. Max 4 TB.
- Data Disk: Additional storage for apps/databases. Max 32 TB each.
- Temporary Disk: Ephemeral storage, auto-created with the VM. Data is wiped if the VM is stopped/deallocated. Only for caching/swap files.
Snapshots
- Point-in-time backup of a single disk.
- Can restore a disk from a snapshot.
- Incremental snapshots save only changed blocks → cost efficient.
Images
- Capture the full state of a VM (OS + data disks + configuration).
- Used to deploy multiple VMs with the same setup.
- Think of an image as a “template” for creating new VMs.
Confusion Buster 🚨
Snapshots vs Images
– Snapshot = backup of a single disk (point-in-time).
– Image = reusable template of an entire VM (can have multiple disks).
Exam trick: If the requirement is “backup a disk,” → Snapshot. If it’s “deploy multiple VMs with same setup,” → Image.
Simple Example
A company runs a SQL database VM. They use Premium SSD for performance. They take daily snapshots for backup. When rolling out 10 identical app servers, they capture an image and deploy from it, instead of configuring each server manually.
Exam Tip
If the question mentions performance-sensitive workloads, the answer is Premium SSD. If it’s low-cost dev/test, pick Standard SSD or HDD. If it’s about backups, think Snapshots. If it’s about mass deployment, think Images.
What to Expect in the Exam
- Direct Q: “Which disk type should you use for production databases?” → Premium SSD.
- Scenario: “Company wants to deploy 10 identical VMs quickly.” → Create an Image.
- Trick Q: “Snapshots can be used to deploy multiple VMs.” (False, that’s Images).