This is a paid asset, but now you can download Server rack / computer servers for FREE, but please remember this package is provided only for learning purposes or to be able to test before buying the product, NOT FOR COMMERCIAL PURPOSES.
Detail this asset from Unity Store: Original Link
Server rack / computer servers v1.0
This is a collection of servers and server racks commonly found in a server room.
The triangle counts for each model range from about 100 –> 800
Many of the models share textures so as to optimize batching performance.
The higher poly models come with a set of LODs that reduce triangle count by about 50% at each LOD stage.
All materials are set up with Unity 5 standard specular shader and come with a diffuse / normal / specular / gloss texture.
Larger objects use 1024×1024 textures while some of the smaller ones use 512×512 textures.