Time To Upgrade: Optimizing Azure VM Performance - Create an Effective PowerShell Script for CPU Usage Monitoring

In this blog post, we will explore a PowerShell script that can be used to monitor the CPU usage of Azure VMs over a specific time period. The script retrieves CPU utilization data for the past 30 days and stores it in a CSV file for further analysis.

Prerequisites

• Azure subscription with access to the VMs you want to monitor

• PowerShell installed and configured with the Azure Az module

Step-by-Step Guide

1. Setting Up the Script

The script utilizes several cmdlets to achieve the desired functionality. Let's break down the script line by line:

$startTime = (Get-Date).AddDays(-30)
$endTime = Get-Date

These lines define the time frame for which we want to collect CPU usage data.

• $startTime is set by subtracting 30 days from the current date using (Get-Date).AddDays(-30).

• $endTime is set to the current date using Get-Date.

1. Initializing Variables

$data = @()
$azVM = Import-Csv ./Inputfile.csv

• $data is an empty array that will be used to store the collected CPU usage data.

• $azVM is a variable that stores the list of VMs to be monitored. This information is assumed to be stored in a CSV file named Inputfile.csv located in the same directory as the script. The Import-Csv cmdlet reads the data from the CSV file.

3. Looping through VMs and Collecting Metrics

foreach($vm in $azVM)
{
  $resourceId = $vm.id
  $metrics = Get-AzMetric -ResourceId $resourceId -MetricName "Percentage CPU" -TimeGrain 00:05:00 -StartTime $startTime -EndTime $endTime -AggregationType Maximum
  $metrics.Data | ForEach-Object {
    $data += [PSCustomObject]@{VM_Name = $vm.Name; Timestamp = $_.TimeStamp; Aggregate_CPU_Max = $_.Maximum}
  }
}

• This foreach loop iterates through each VM listed in the $azVM variable.

• Inside the loop, the $resourceId variable stores the unique identifier of the current VM being processed.

• The Get-AzMetric cmdlet retrieves CPU usage metrics for the VM. Here's a breakdown of the parameters used:

• ResourceId: The ID of the Azure VM resource.

• MetricName: The specific metric to retrieve, which is "Percentage CPU" in this case.

• TimeGrain: The time interval for each data point. Here, it's set to 5 minutes (00:05:00).

• StartTime: The starting point of the time range for which to collect data (as defined by $startTime).

• EndTime: The ending point of the time range for which to collect data (as defined by $endTime).

• AggregationType: The type of aggregation to apply to the data points. Here, we're using Maximum to get the peak CPU usage within each time interval.

• The output of Get-AzMetric is piped to the ForEach-Object cmdlet. This further iterates through each data point retrieved for the current VM.

• Inside the inner loop, a new custom object is created using [PSCustomObject] and added to the $data array. This object stores three properties:

• VM_Name: The name of the virtual machine.

• Timestamp: The date and time for the data point.

• Aggregate_CPU_Max: The maximum CPU usage for the corresponding time interval.

4. Exporting the Data

$data | Export-csv ./Percentage_CPU_Output.csv

• Finally, the $data array containing the collected CPU usage information for all VMs is exported to a CSV file named Percentage_CPU_Output.csv using the Export-Csv cmdlet. This file can be used for further analysis or visualization of the CPU usage trends.

This PowerShell script provides a convenient way to monitor and track the CPU usage of your Azure VMs over a specified time period. By customizing the script's parameters, you can adjust the time range, metric name, and output file name to suit your specific needs. Remember to replace