Once, long ago, men carved their knowledge into the walls of caves so that it would be available for all time. Unfortunately, their knowledge was tied to once place. Eventually, a forward thinking cave dweller thought about carving his knowledge into a clay tablet. He was savagely beaten to death and his family burned as witches. Eventually the other cave dwellers realized that it was probably a good idea to have a more portable way to store their knowledge and they too adopted this portable clay-based knowledge transfer system. Fast forward to the tail end of 2010 and people are saying that Microsoft has got it wrong with the Azure VM role. People are already lambasting it as a laughable concept that’s needlessly complex to patch. I can’t argue with that, it is complex to patch, but there’s a reason for that complexity and it’s called stateless computing. It’s like the switch from procedural/object-oriented programming to functional programming. When you first switch, you get pissed off that you can’t reassign variables and that functions can’t have side effects. You get used to that pretty quickly and start doing crazy things with tail recursion and other functional paradigms that ultimately save you memory. remove debugging headaches, and give you an incredible amount of computing stability. With the last paragraph in mind, let’s look at Azure VMs again – we can’t patch the VM directly. It’s stateless. What does a stateless VM buy you?
- It’s easy to spin up additional, identical VMs. There’s no worrying if some master image is the same: it is.
- It’s easy to back out incompatible patches – just remove the differencing VHD.
- There are no side effects because of errant garbage living on the C: drive.
- Security – if a virus infects your VM, just reboot.
- Complex, time consuming patches can be applied once and quickly moved into place.
- There’s a load balancer in front of every Azure instance. Operations must be idempotent, even when executed against different instances.
Managing state isn’t a component of your operating system in Azure, it’s a component of the storage tier. New paradigms require new ways of thinking. Sometimes a new way of thinking seems broken, wrong, or foolish. If you’re looking to customize your Azure deployment stack without sacrificing the flexibility of using Azure, then Azure VM roles are for you. If you’re looking for a replacement for your current VM Ware installation, Microsoft’s Azure VM roles aren’t for you. But while you’re fiddling around with VM settings, I’m going to be playing Scrabble.