- Install RAM, SSD's, HDD's
- Mass-deploy servers via imaging processes
- Network configuration issues (TCP/IP)
- Network infrastructure issues (cabling, switch ports, etc)
- Adjusting firewall configurations
- Bad hardware (bad optics, server components, etc)
I can confirm this (I work at MacStadium). We've got 1. a large number of CI SaaS companies that run their OS X/iOS builds on our hardware and 2. at least several hundred companies that run their own custom build tools or Jenkins on individual or clusters of Mac minis, Xserves, and Mac Pros in our data centers.