Creating a PowerShell script to power on multiple VMs in a VMware environment after a power outage involves using VMware PowerCLI, a module that provides a powerful set of tools for managing VMware environments. Below, I’ll outline a basic script for this purpose and then discuss some best practices for automatically powering on VMs.

PowerShell Script to Power On Multiple VMs

Install VMware PowerCLI: First, you need to install VMware PowerCLI if you haven’t already. You can do this via PowerShell:

Install-Module -Name VMware.PowerCLI

Connect to the VMware vCenter Server:

Connect-VIServer -Server "your_vcenter_server" -User "username" -Password "password"

Script to Power On VMs:

# List of VMs to start, you can modify this to select VMs based on criteria
$vmList = Get-VM | Where-Object { $_.PowerState -eq "PoweredOff" }

# Loop through each VM and start it
foreach ($vm in $vmList) {
    Start-VM -VM $vm -Confirm:$false
    Write-Host "Powered on VM:" $vm.Name
}

Disconnect from the vCenter Server:

Disconnect-VIServer -Server "your_vcenter_server" -Confirm:$false

Best Practices for Automatically Powering On VMs

1. VMware HA (High Availability):
   • Use VMware HA to automatically restart VMs on other available hosts in case of host failure.
   • Ensure that HA is properly configured and tested.
2. Auto-Start Policy:
   • Configure auto-start and auto-stop policies in the host settings.
   • Prioritize VMs so critical ones start first.
3. Scheduled Tasks:
   • For scenarios like power outages, you can schedule tasks to check the power status of VMs and start them if needed.
4. Power Management:
   • Implement UPS (Uninterruptible Power Supply) systems to handle short-term power outages.
   • Ensure your data center has a proper power backup system.
5. Regular Testing:
   • Regularly test your power-on scripts and HA configurations to ensure they work as expected during an actual power outage.
6. Monitoring and Alerts:
   • Set up monitoring and alerts for VM and host statuses.
   • Automatically notify administrators of power outages and the status of VMs.
7. Documentation:
   • Keep detailed documentation of your power-on procedures, configurations, and dependencies.
8. Security Considerations:
   • Ensure that scripts and automated tools adhere to your organization’s security policies.