The HP Z220 was designed for a corporate environment, where downtime just isn't tolerated.
I've read the user manual once so far, and it's amazing.
It can be, and obviously was, used with a PxE boot scheme.
The refurbishers seemed pretty limited in understanding details like that,
or setting it up to boot from a hard drive, or much of anything 'technical'.
If I read right, the computer can be remotely shut down, started, rebooted, updated, whatever.
When that fails, you send in your parts changer, and expect his/her immediate return with the unsat part.
All the parts except the motherboard can be replaced in seconds without tools. You just grab the latch on the cover, and pull up to open and remove it.
Then the power supply and the drives sort of tilt up like little dump trucks, and everything just unplugs.
Even the cards that plug into the motherboard are retained by a fancy multiple clamp, no screws.
It's a pretty sophisticated piece of mechanical engineering.
Mike Halloran
Corinth, NY, USA