A rack and tower server are fundamentally the same – just one is in an upright/vertical position and the other is in a horizontal position.

Both types can usually accommodate similar components – they can all have a single or dual socket motherboard – all can have a single or redundant psu and all have various cooling options to suit the components that go within.

The benefit of a tower system though is they are compact and thought has been put into the cooling of them for quiet operation as most tower systems are used within an open office – not very often in a cupboard or out of sight. Tower systems often have a lockable door, too, to help reduce unwanted access, usually again due to them being in an open office.

The benefit of a rack system is density. Tower systems are generally all the same width, height and length. However, a rack system while the same width, can often be much less tall – but fit the same number of components within.

In fact, when it comes to the number of hot-swap drive bays, a rack system tramps all over the towers. Tower systems generally only have a small number of hot-swap bays -usually up to 8 bays. However, in a rack system, in the same physical size (but horizontal orientation), you can have up to 36 bays (24x at the front and 12x at the rear).

It should also be noted that rack systems are generally not installed in an office where others work – they usually go into a server cabinet in another room to keep them both physically and audibly isolated. Rack servers don’t have any thought put into them to keep them quiet as a result of their segregation from those who could hear them. This is done to maximise the cooling efficiency.