Servers are generally placed on racks (also called cabinets).

A common standard rack is usually 42U in height. U is a unit that represents the external dimensions of the server and is the abbreviation of unit. 1U is equal to 4.445cm. As for the rack width, it is 600mm or 800mm.

There are many types of rack depths, including 600mm, 800mm, 900mm, 1000mm, 1200mm, etc. Generally speaking, IT equipment (server) racks are deeper (1100mm or 1200mm), while communication equipment racks are shallower (600mm).

In addition to servers, the IT equipment in the rack also includes professional storage devices such as disk arrays.

Nowadays, big data is being talked about everywhere. The amount of data generated by us humans is increasing every year, which also increases the number and performance requirements for storage devices.

Everyone should know that the current mainstream computer storage hard drives are divided into two types: HDD and SSD. HDD is our traditional mechanical hard drive, while SSD is a solid-state drive that is gradually becoming more popular.

SSD is a semiconductor memory with fast storage speed and small size, so it is very popular. However, it is expensive. For data centers, HDD is still the mainstream choice due to cost-effectiveness considerations. SSDs are currently mainly used for high-end customers and businesses that require high performance.

In addition to IT computing equipment, there are also data communication equipment such as switches, routers, and firewalls.

When it comes to switches, a term must be mentioned - TOR, Top of Rack.

TOR switch is a common term in the data center field. As the name suggests, it means the switch at the top of the rack. This type of switch is the lowest network switching device in the data center. It is responsible for connecting the servers inside the rack and connecting to the upper-level switches.

In fact, the rack switch does not say that it must be placed on the top of the rack. It can be at the top of the rack, or in the middle or bottom of the rack. It is usually placed at the top simply because it is most conducive to internal wiring.

Further up the rack, there are a row of racks and N rows of racks. To connect these racks and servers, data center networking technology is required.

The most popular data center networking architecture now is Spine-Leaf. I have an article dedicated to introducing it, so I won’t go into nonsense here.