Looking inside our Dell PowerEdge R220 we can see a relatively well laid out design. There are a total of four fans cooling which spreads enough airflow around the short depth chassis.
Underneath the CPU and memory shroud we can find the LGA1150 socket, passive heatsink and four RAM slots that accept up to 32GB. The dual chassis fans provide redundancy in the event of a failure so that air will still move through the shroud.

Next the CPU and memory is an internal USB type-A header. In the example below we used a SanDisk CZ43 as an ESXi boot drive. Certainly a nice touch for embedded OSes.
There is a single PCIe expansion slot in the chassis and plenty of room for most add-in networking or storage cards. We fit NVMe drives as well as network cards like Mallanox dual port FDR Infiniband cards in the riser.

The rear of the Dell PowerEdge R220 had a number of ports on the back. There were legacy VGA and serial ports. Two USB 3.0 ports provided more modern connectivity. The R220 also had front I/O for VGA and USB to aid in the use of KVM carts in the datacenter. One can see two Broadcom based gigabit Ethernet ports. One unusual feature was the eSATA port which can be used for external expansion for those that shun the use of NAS storage. Finally the 80 Plus Silver power supply had a nice feature on the rear I/O panel: a cable management clip. That black clip on the right side of the image helps keep the cabling more organized which is important in the datacenter.