Blade Server Vs. Rack Server: The Differences Explained

The decision of blade server vs. rack server, the most common type of server, is an important one. To make the right choice, you’ll need to pay attention to the pros and cons of each and how they complement or challenge your needs. 

Many vendors offer both types of servers through different series and models. So, choosing one can be understandably difficult.

In this article, we will provide the following:

• A detailed comparison between blade and rack servers.
• An explanation of the differences between the two.
• How to make the best choice when procuring servers for your enterprise.

What Is A Blade Server?

A blade server is a small, modular server housed in server bays. Besides the CPU, memory, and network controllers, these servers may also have storage built-in. However, any other components the server needs must be housed in the server chassis where all the blade servers go. 

In other words, blade servers share power and other resources via the server chassis. This allows them to be smaller in size. A blade server bay or rack can house more units efficiently — for instance, a blade server bay can hold up to 20 servers. The bay can even be mounted onto a rack, allowing for more density. 

What Is A Rack Server?

A rack or rack-mounted server is a server made to be mounted on a rack. A server rack is an enclosure that houses servers and other equipment (for example, storage). As a result, these servers have standard dimensions so they can fit into the rack. 

Rack servers can be stacked easily, allowing a rack to house multiple servers, typically up to 10. The rack is configured with peripherals to control and manage the individual servers. Although smaller than traditional tower servers, these servers can have more internal components, including graphics, video cards, and power supplies. 

Rack servers are commonly used in data centers because of the standard dimensions, smaller footprint, and installation convenience. 

Difference Between Blade And Rack Server

Here are the main differences between rack and blade servers that ultimately contribute to their feasibility for different use cases. 

Design

The primary difference between blade and rack servers is their design. Blade servers are modular and designed with a circuit board that shares multiple components like CPU, memory, storage, et cetera. 

On the other hand, rack servers have a bigger form factor as they have more architecture components. They are standalone servers that can run independently, unlike blade servers that take power from the chassis. 

Density

Although rack and blade servers offer higher density than tower servers, blade servers are best for high-density data centers. Their design allows for more units to be housed in a smaller space. 

Rack servers are also dense by design, as you can mount multiple in a single rack. However, unlike blade servers, they don’t offer the same level of density, which means they require more space than blade servers. 

Power

In blade servers, the chassis is fitted with power supply components, so all the servers share the power supply in the server bay. While this design saves cost, it also impacts reliability because if the power supply fails, all servers housed in the chassis will be affected. 

In the case of rack servers, the power supply may be shared or made redundant for each server. In the latter case, the reliability is higher, as failure in the power supply for one unit doesn’t necessarily impact other units in the rack. 

Compared with blade servers, rack servers have a higher power draw. 

Cooling

Because of their high-density design, blade and rack servers can produce a lot of heat. So, both of these server types require constant cooling and temperature management. 

Cooling rack servers are relatively easier as they have built-in fans. Also, other cooling components can be configured in the rack itself. 

Customization

Regarding customizability, blade servers are comparatively easier to customize. So for enterprises looking to customize the design and components of their servers, blade architecture is the better choice. As a result, these servers can be customized to handle specific workloads, for example, compute-intense AI workloads. 

Rack servers can also be customized, but not to the degree and convenience of blade server bays. 

Maintenance

Blade servers are modular, so they’re hot-swappable. This means a server can be removed and replaced from a cluster without powering down the other servers in the chassis. So, should a component or entire server fail, it can be removed from the bay easily. 

Rack servers are easy to maintain but may induce some downtime, depending on the configuration of the rack. Moreover, racks can be large and house different appliances, complicating the replacement efforts. 

Cost

The price of a server depends on a variety of factors. Generally speaking, rack servers are cheaper. Blade servers require a dedicated chassis, which adds to the production cost. However, they can be cost-effective because of their high density. 

Both blade and rack servers call for cooling infrastructure. The former does require more cooling provisions, so that should also be factored into the operational expenses of these servers. 

Benefits Of Blade Servers

Here are the advantages of blade servers summarized:

• Modular design: The modular design of blade servers offers high density per rack, making the servers more customizable. 
  
  
• Easy to maintain: As these servers can be hot-swappable, maintaining them is super easy and doesn’t require any downtime for other servers. 
  
  
• Fewer cables: The design of blade servers in a chassis reduces the need for cables. This makes them more manageable. 
  
  
• Higher processing power: Blade servers can have higher processing power (more CPUs) as they don’t contain other typical components that come built-in in rack or tower servers. 

Benefits Of Rack Servers

Here are the advantages of rack-mounted servers:

• Convenience: As rack servers are more standardized, especially in data centers, they offer the convenience of installation and configuration. 
  
  
• Reliable power: As power supply units are often built-in, rack servers are more reliable. They can run as standalone servers if need be. 
  
  
• Cooling: Rack servers are relatively easier to cool due to a lesser density than blade servers and built-in fans. 

Blade Vs. Rack Server: Which One Should You Choose?

In data centers, rack servers have been ubiquitous because of their configuration and ease of scalability. However, blade servers are gradually gaining momentum in the data center space because of their high computing power. 

Blade servers are a suitable choice for large processing clusters, the kind needed for handling complex workloads. Enterprises that require more processing from their servers should lean toward blade clusters. The customizability, of course, is an added advantage. 

Remember that they produce a lot of heat, so they require dedicated cooling solutions that prevent equipment damage. 

Blade servers are also a good option if you’re pressed for floor/rack space. 

For traditional data centers that handle data storage primarily, rack servers are the undisputed choice. They’re cheaper, last many years, and can be maintained easily. 

Rack servers are also good for smaller deployments, for example, server rooms in branch offices. They can be configured according to your needs rather easily. 

Procuring The Best Servers

The differences are plentiful when making the choice between a blade server vs. a rack server. You should choose the kind that meets your business and technical needs, but no matter what type of server you choose, you must do your homework before settling on a brand and model. 

Buying servers is a significant investment that should consider your budget and overall IT strategy. 

At PivIT, we help procure new and legacy servers per our client's needs and preferences. With a no-strings-attached approach, our procurement specialists can help you procure the necessary equipment without crossing your budget. 

With a large network of manufacturers, PivIT offers an extensive selection of servers — both new and legacy — to help connect virtually any kind of network. We are here to help you make sharing, storing, and accessing your data as simple as possible.