Rightsizing Azure VMs with Advisor

Introduction

In today's cloud-first world, optimizing resource utilization is paramount for both financial prudence and operational efficiency. Azure Virtual Machines (VMs) provide the backbone for countless applications, but their inherent flexibility also presents a challenge: ensuring they are neither over-provisioned (leading to unnecessary costs) nor under-provisioned (resulting in performance bottlenecks). This article delves into the critical practice of rightsizing Azure VMs, focusing on how Azure Advisor, Microsoft's personalized cloud consultant, can be leveraged to achieve this balance effectively.

Rightsizing isn't merely about cutting costs; it's about aligning your VM resources precisely with the actual workload demands. This ensures your applications perform optimally without incurring wasteful expenditure on unused CPU, memory, or storage. This guide is intended for cloud architects, Azure administrators, financial operations (FinOps) professionals, and anyone responsible for managing the cost and performance of Azure infrastructure.

Why this matters

The benefits of proper VM rightsizing extend far beyond mere cost savings, impacting various aspects of an organization's cloud strategy. From a financial perspective, overprovisioned VMs directly translate to inflated Azure bills, diverting budget from other strategic initiatives. Compliance, particularly for regulated industries, often mandates efficient resource management and auditing, making rightsizing an integral part of maintaining a compliant cloud footprint.

Technically, correctly sized VMs reduce resource contention, improve application response times, and enhance overall system stability. Under-provisioned VMs, conversely, lead to poor user experience, increased support incidents, and potential application failures. Rightsizing also plays a crucial role in managing risk by preventing performance-related outages and ensuring business continuity. By proactively adjusting VM sizes, organizations can improve their operational productivity and free up engineering time previously spent fire-fighting performance issues.

Key concepts

• Azure Advisor: A personalized cloud consultant that helps you follow best practices to optimize your Azure deployments. It analyzes your resource configuration and usage telemetry and recommends solutions that can help improve the reliability, security, operational excellence, performance, and cost-effectiveness of your Azure resources.
• Cost Recommendations (Azure Advisor): A specific category within Azure Advisor that identifies idle or underutilized resources and suggests ways to reduce spending. For VMs, this typically involves recommendations to resize or shut down instances.
• VM Utilization Metrics: Key performance indicators (KPIs) such as CPU utilization percentage, memory usage, disk I/O operations per second (IOPS), and network input/output that provide insights into how a VM is performing relative to its allocated resources. Azure Monitor collects these metrics.
• Virtual Machine Scale Sets (VMSS): A feature that allows you to create and manage a group of load-balanced VMs. Rightsizing recommendations can also apply to individual instances within a scale set.
• Reserved Instances (RIs): A pricing model that provides a significant discount compared to pay-as-you-go pricing for specific VM sizes, but requires a commitment for a 1-year or 3-year term. Rightsizing before purchasing RIs is crucial to avoid locking into an oversized commitment.

Step-by-step implementation

Implementing rightsizing recommendations from Azure Advisor involves a systematic approach, typically starting with identification and ending with validation.

1. Access Azure Advisor:

Navigate to the [Azure portal](https://portal.azure.com). Search for "Advisor" in the global search bar and select "Advisor".

1. Review Cost Recommendations:

Within Advisor, select the "Cost" blade from the left-hand navigation. Filter the recommendations by "Virtual Machines" or review all recommendations. Look for suggestions like "Right-size or shut down underutilized virtual machines."

1. Analyze Specific VM Recommendations:

Click on a specific VM recommendation to view details. This will often show the historical CPU and memory utilization, the recommended new VM size, and the estimated monthly savings. Consider the utilization trend over a significant period (e.g., 7, 30, or 90 days) to avoid rightsizing based on anomalous short-term spikes.

1. Validate Workload Requirements:

Before implementing a change, confirm the application's actual resource requirements with application owners or developers. Azure Advisor provides data, but contextual understanding of critical business events (month-end processes, seasonal peaks) is essential. Check for any specific software vendor requirements for minimum VM sizes.

1. Resize the VM (if recommended and validated):

If the recommendation is solid, you can initiate the resize process directly from the Azure portal by navigating to the VM, selecting "Size" under "Settings," and choosing the new size. For automation or bulk operations, PowerShell or Azure CLI is effective.

```powershell # Connect to Azure Connect-AzAccount

# Define parameters for the VM to resize $resourceGroupName = "myResourceGroup" $vmName = "myVM" $newVmSize = "Standard_B2s" # Example recommended size from Advisor

# Get the current VM object $vm = Get-AzVM -ResourceGroupName $resourceGroupName -Name $vmName

# Stop the VM before resizing (usually required for size changes involving CPU/memory changes) Stop-AzVM -ResourceGroupName $resourceGroupName -Name $vmName -Force

# Update the VM size property $vm.HardwareProfile.VmSize = $newVmSize

# Update the VM in Azure Update-AzVM -ResourceGroupName $resourceGroupName -VM $vm

# Start the VM after resizing Start-AzVM -ResourceGroupName $resourceGroupName -Name $vmName

Write-Host "VM '$vmName' in resource group '$resourceGroupName' has been resized to '$newVmSize'." ```

1. Monitor Post-Resize Performance:

* After resizing, closely monitor the VM's performance using Azure Monitor metrics for CPU, memory, and disk I/O to ensure the new size meets the workload demands without degradation.

Example configuration

While direct configuration snippets for rightsizing are often imperative commands (as seen in the PowerShell example), here's a Bicep example showing how you might define a VM with a specific size, which would then be subject to Advisor's recommendations. Rightsizing typically involves modifying this vmSize property.

resource virtualMachine 'Microsoft.Compute/virtualMachines@2023-03-01' = {
  name: vmName
  location: location
  properties: {
    hardwareProfile: {
      vmSize: 'Standard_D2s_v3' // Advisor might recommend changing this to a smaller size like 'Standard_B2ms'
    }
    osProfile: {
      computerName: vmName
      adminUsername: adminUsername
      adminPassword: adminPassword
    }
    storageProfile: {
      imageReference: {
        publisher: 'MicrosoftWindowsServer'
        offer: 'WindowsServer'
        sku: '2022-Datacenter'
        version: 'latest'
      }
      osDisk: {
        createOption: 'FromImage'
        managedDisk: {
          storageAccountType: 'Standard_LRS'
        }
      }
    }
    networkProfile: {
      networkInterfaces: [
        {
          id: nic.id
        }
      ]
    }
  }
}

Common pitfalls

• Ignoring workload seasonality: Rightsizing based on off-peak utilization can lead to performance issues during peak periods. Always consider the historical utilization over a complete business cycle.
• Solely trusting Advisor without validation: Azure Advisor provides data-driven recommendations, but it lacks application context. Always validate with application owners and understand any specific software requirements or licensing implications.
• Neglecting dependencies: Resizing a VM might impact other services or applications that depend on its specific performance characteristics or IP address (though IP often persists, performance changes can break things).
• Focusing only on CPU: While CPU is a common bottleneck, memory, disk I/O, and network throughput are equally critical. An application might be CPU underutilized but memory-starved. Azure Advisor typically considers all these factors.
• Failing to monitor post-resize: Without monitoring, you cannot confirm if the new size is adequate, potentially leading back to the original problems (over/under-provisioning).
• Resizing critical production VMs during business hours: This can lead to downtime for the application, impacting business operations. Schedule changes during maintenance windows.

Best practices

• Implement a phased approach: Start with non-production environments (dev/test) to validate rightsizing changes and build confidence before applying them to production systems. This aligns with the Azure Well-Architected Framework's reliability pillar.
• Automate monitoring and alerts: Set up Azure Monitor alerts for CPU, memory, and disk utilization to proactively identify both over and under-provisioned VMs.
• Establish a FinOps culture: Integrate rightsizing into your financial management processes. Regularly review Advisor recommendations as part of your cloud cost optimization initiatives. This aligns with the principles of the Cloud Adoption Framework's Operate methodology.
• Document and review: Maintain clear documentation of VM rightsizing decisions, including the rationale, date, and impact. Regularly review these decisions as application requirements evolve.
• Consider Azure Autoscale for variable workloads: For workloads with highly fluctuating demands, Azure Autoscale for VM Scale Sets can dynamically adjust instances, providing a more agile rightsizing solution than manual intervention.
• Leverage Azure Advisor Score: Periodically review your Azure Advisor Score to track progress on cost optimization and other best practices. Aim for continuous improvement.

Further reading

• Optimize and reduce spend with Azure Advisor
• Cost recommendations for Azure Virtual Machines
• How to delete or resize an Azure virtual machine
• Introduction to the Azure Well-Architected Framework
• Cloud Adoption Framework for Azure - Optimize costs