Dell Optiplex Rackmount Server
This Dell Optiplex MFF Micro Form Factor rackmount has provisions for Cat6 patch-thru keystones. and a pocket for an external HDD. This will allow a MFF PC to be used as a server. Be sure to push straight down and latch both sides at the same time with a VERY FIRM push with hammer or palm of gloved hand. These were designed to fit VERY snug and perfectly flush on the face of the mount.
I used these as the keystones:
https://www.amazon.com/gp/product/B075ZPGV1H
I used this external HDD:
https://www.amazon.com/WD-5Tb-My-Passport-Ultra-Portable-External-Drive/dp/B07X46C64N