Add data disks

When managing virtual machines (VMs) in Azure, one of the key tasks an Azure Administrator must be familiar with is the addition of data disks to existing VMs. This capability is crucial for scenarios where additional storage space or optimized disk performance is required.

Understanding Data Disks in Azure

In Azure, a data disk is a VHD (Virtual Hard Disk) that’s attached to a VM to store application data, or other data you need to keep. These disks are registered as SCSI drives and are labeled with a letter that you choose. Each data disk has a maximum capacity of 32,767 gibibytes.

Azure offers several types of data disks that vary in performance and pricing:

• Standard HDD: Best for infrequent access or where cost is a priority.
• Standard SSD: Balanced performance and cost, suitable for web servers, low IOPS application servers.
• Premium SSD: High-performance SSD suitable for production and performance-sensitive workloads.
• Ultra Disk: Highly flexible performance and IOPS, suitable for data-intensive workloads such as SAP HANA, top-tier databases, and transaction-heavy workloads.

The type of disk you choose will depend on the performance and cost needs of your application.

Adding a New Data Disk to an Azure VM

To add a new data disk to an Azure VM, follow these general steps:

1. Select the Azure VM: Go to the Azure portal, select the desired virtual machine, and click on the option ‘Disks’ from the sidebar.
2. Add Data Disk: Click on the ‘+ Add data disk’ button to create a new disk. You’ll be prompted to configure the new disk options.
3. Configure the Disk: Choose the disk type (HDD, SSD, or Ultra Disk), size, and other configuration settings like encryption, host caching.
4. Name the Disk: Provide a name for the disk and Azure will create a VHD and attach it to the VM.
5. Save Configuration: Once you’re done with the configuration, click the ‘Save’ button to apply the changes and attach the new data disk to the VM.

Initializing and Partitioning the Data Disk in Windows VMs

Once the disk is attached, you need to initialize and partition it:

1. Connect to your Azure VM using Remote Desktop.
2. Open the Disk Management tool.
3. Initialize the disk (MBR or GPT) as it will appear as ‘Unknown’ and ‘Not Initialized’.
4. Create a new simple volume, assign a drive letter, and format the partition.

For Linux VMs, you’d use the fdisk or parted utilities to partition the new disk and then format it using the appropriate filesystem type (e.g., ext4, xfs).

Automation and Management with Azure CLI and PowerShell

Azure CLI and PowerShell cmdlets enable the automation of data disk addition:

• Azure CLI: Use the az vm disk attach command to create and attach a new data disk to a VM.
• PowerShell: Use the Add-AzVMDataDisk cmdlet to add a new data disk to a VM.

Scaling and Performance

It’s crucial to consider the size of the VM when adding data disks, as the size affects the number of data disks you can attach and the performance:

• I/O throughput and the number of IOPS (Input/Output Operations Per Second) are capped based on the size of the VM.
• Standard VMs offer limited IOPS, whereas the latest DS series VMs provide better performance.
• The following table illustrates an example of the data disk scaling based on VM size:

Best Practices

• Always keep data and OS disks separate to maximize performance and management.
• Use Azure Backup to protect the data on your disks.
• Leverage Azure Managed Disks for better scaling, management, and security.

Conclusion

Adding data disks to Azure VMs expands their storage capacity and performance. Whether it’s for a standard workload or a high-demand application, Azure has the disk options to meet every need. Azure Administrators must be familiar with the process of adding, initializing, and configuring data disks to ensure efficient storage management in their Azure infrastructure.