Parts of a Server – Drives, Fans, Memory and Power

All 13 parts on the diagram

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Cover off, from above 8

Hard drives Each sits in a carrier. The carrier slides out of its bay from the front.
Backplane Cables run from it to the system board and the storage controller.
Fans In many servers a fan can be changed while the server runs.
Heat sink This server has two processors, so it has two heat sinks.
Memory modules They are also called DIMMs.
System board It is the server's motherboard.
Power supplies Servers often have two. One can fail and the server keeps running.
Expansion card riser One manual calls it a riser and the other a riser cage.

Front and back panels 5

Power button On some servers it is called the power on and standby button.
Optical drive It is a slimline drive. It is thin enough to share the front with the drive bays.
Expansion slots The slots belong to the risers inside. A card in a slot shows its end here.
Video connector Both manuals read for this page show one on the back panel.
NIC connectors NIC stands for network interface controller. A server usually has several.

How this list was compiled: Every name checked on 2026-09-30, a name kept only where two independent sources use it: a server maker's hardware owner's manual with a figure of the inside of the system, https://archive.org/details/manualsbase-id-69720 (hard drives, SAS backplane, hot-swappable cooling fans, processors and heat sinks, memory modules, system board, power supplies, expansion-card riser, expansion slots, optical drive, power button, video connector, NIC connectors); a second maker's server user guide, https://archive.org/details/manualzilla-id-6924056 (hard drives and hard drive bays, SAS backplane, hot-plug fans, processor and heatsink, DIMMs, system board, power supply, PCI riser cage, expansion slots, optical drive, the power button, video connector, NIC connectors); and Wikipedia, text only, Server (computing), https://en.wikipedia.org/wiki/Server_(computing) (dual power supplies as redundancy, hot swappable parts, fans) and Backplane, https://en.wikipedia.org/wiki/Backplane. Hints and detail lines are in our own words. Licence: own work

The drawing: Drawn for this site on 2026-09-30 from plain geometry; a generic server, no maker's layout, nothing traced. Licence: own work

How it works

A rack server is a wide, flat computer built to slide into a rack. With the cover off, its parts sit in order from front to back, the way the air flows through it.

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Inside, from front to back

The hard drives are at the front and plug into the backplane. Behind it a row of fans blows over two heat sinks, each on a processor, with memory modules beside them on the system board. At the back are two power supplies and a riser that holds the expansion cards flat.

The front and back panels

The front has the power button, an optical drive and the drive bays. The back has the expansion slots, a video connector, the NIC connectors for network cables and the ends of the power supplies.

Front or back? Drives come out of the front. Power cords and network cables plug in at the back.

Questions and answers

What are the main parts of a server?

Processors under heat sinks, memory modules, a system board, hard drives, fans and one or two power supplies. A rack server adds a backplane behind the drives and a riser for expansion cards.

Why does a server have two power supplies?

For redundancy. Servers often have dual power supplies so that one can fail, or be changed, without the server shutting down.

What is a backplane in a server?

A board with a row of connectors that the hard drives plug straight into when they slide into their bays. Cables link it to the rest of the server.

How is a server different from a desktop computer inside?

The same kinds of parts are there, but a server often has two processors, many memory modules, stronger fans, spare power supplies and parts that can be swapped while it runs.