Use 3rd party storage as primary OS X server storage or hire OS X server?
You can probably hire a server from https://macminicolo.net/ or by finding a consultant at https://locate.apple.com

You certainly can have the Mac running server app use all manner of third party storage whether it's DAS, NAS or also cloud (private or public) since the file sharing capabilities are quite full featured as is the OS in utilizing various storage technologies.