When adding a data disk to your Azure VM, the choice of disk type directly impacts performance, throughput, and latency. Azure offers several disk types, each designed for different workloads. To make the right selection, follow these steps:

Step 1: Assess Your Workload Requirements

Begin by analyzing the nature of your workload.

  • If your application is latency‑sensitive (like SQL Server, SAP HANA, or OLTP databases), you need disks that guarantee sub‑millisecond response times.
  • If your workload is throughput‑intensive (like analytics or big data), focus on disks that can deliver high MB/s transfer rates.
  • For backup or archival workloads, prioritize cost efficiency over performance.

Step 2: Match Disk Type to Workload

  • Premium SSDs are the default choice for most production workloads. They provide consistently low latency (under 1 millisecond) and high IOPS, making them ideal for databases and enterprise applications.
  • Ultra Disks are designed for mission‑critical workloads requiring extremely high performance. They allow you to configure IOPS and throughput independently, which is useful for applications with unpredictable or very demanding requirements.
  • Standard SSDs offer moderate performance and are suitable for web servers or lightly used applications where latency is less critical.
  • Standard HDDs are best for infrequent access workloads such as backups, test environments, or archival storage.

Step 3: Choose the Right Disk Size

Disk performance in Azure scales with size. Larger disks support higher IOPS and throughput. For example, a 1 TB Premium SSD offers significantly more performance than a 128 GB Premium SSD. Always size disks based on both capacity and performance needs.

Step 4: Configure Caching Appropriately

Azure allows you to configure caching for attached disks.

  • Use Read‑only caching for workloads that are read‑heavy, such as web applications serving static content.
  • Disable caching for write‑intensive workloads like transactional databases to avoid data consistency issues.

Step 5: Monitor and Validate Performance

After attaching the disk, monitor performance using Azure Monitor and Windows tools. Track metrics such as IOPS, throughput, and latency. If performance does not meet expectations, consider resizing the disk, changing the disk type, or distributing workloads across multiple disks.

Best Practices

  • Always benchmark your workload before finalizing disk type.
  • For production workloads, prioritize Premium SSDs or Ultra Disks to ensure predictable performance.
  • Distribute heavy workloads across multiple disks to avoid bottlenecks.
  • Use Azure Advisor recommendations to optimize disk usage and cost.
  • Regularly review metrics and adjust disk configuration as workloads evolve.