As with any managed services or infrastructure services projects, maintaining the server inventory is very crucial. The server-inventory-file provides a one-stop checklist, that you can refer while you are on priority 1 bridge calls.
With a traditional data center, it is easy to maintain server/infra inventory on an excel sheet. But it is not the same with the cloud because the infrastructure is so dynamic.
The only solution to this problem is Automation. I have written a PowerShell script just to do that.
Below is the link to the script:
https://gallery.technet.microsoft.com/scriptcenter/Powershell-Script-to-4e623057
Also, check out my blog for Azure Inventory:
https://manjunathrao.com/2016/12/30/powershell-generate-azure-inventory/
https://manjunathrao.com/2017/12/04/powershell-generte-azure-paas-inventory/
If this blog helps even one person on this planet. The purpose of this blog is served.