PowerShell versus ARM Templates

Let me explain why complete PowerShell deployment would be too slow, and how ARM/JSON is they best way to deploy things in Azure.

With PowerShell you describe the deployment process, one step at a time, connecting each and every dot. The deployment is serialized, with no parallelism unless you use PowerShell features to run parallel jobs. The result isn’t much faster than you doing all the clicking for yourself.

ARM or JSON templates describe the result, not the process. Once you submit the deployment, ARM divides up the job and orders the deployment based on your dependencies. That means that the deployment can be parallelized. If I need 100 web servers, all 100 will be deployed at once, not in some 1..100 loop, one at a time (or 5 at a time if you are clever).

PowerShell Still Required

PowerShell is still very useful for some fiddly deployment things that don’t have ARM options, or are once-offs and don’t have a GUI option. To be honest, I do use GUI for most of my once-offs because it is convenient and gets the end result faster than researching/tweaking/fixing PowerShell examples. When it comes to learning about settings and troubleshooting, PowerShell can be pretty awesome.

But PowerShell is much slower than ARM for deployments.