Kelly has an interesting post about memory mapped files and the cloud. This is in response to a comment on my post where I stated that we don't reserve space up front in Voron because we support cloud providers that charge per storage.
From Kelly's post, I assume she thinks about running it herself on her own cloud instances, and that is what here pricing indicates. Indeed, if you want to get a 100GB cloud disk from pretty much anywhere, you'll pay for the full 100GB disk from day 1. But that isn't the scenario that I actually had in mind.
I was thinking about the cloud providers. Imagine that you want to go to RavenHQ, and get a db there. You sigh up for a 2 GB plan, and all if great. Except that on the very first write, we allocate a fixed 10 GB, and you start paying overage charges. This isn't what you pay when you run on your own hardware. This is what you would have to deal with as a cloud DBaaS provider, and as a consumer of such a service.
That aside, let me deal a bit with the issues of memory mapped files & sparse files. I created 6 sparse files, each of them 128GB in size in my E drive.
As you can see, this is a 300GB disk, but I just "allocated" 640GB of space in it.
Read more: Ayende @ Rahien