Hardware Load Balancer

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Hardware Load Balancer Definition

A hardware load balancer, also known as a hardware load balancing device (HLD), is a proprietary appliance built on custom ASICs to distribute traffic across multiple application servers on the network.

Diagram depicting hardware load balancing with the image of end users to a hardware load balancer to the application servers.


What is a Hardware Load Balancer?

A hardware load balancer is a hardware device with a specialized operating system that distributes web application traffic across a cluster of application servers. To ensure optimal performance, the hardware load balancer distributes traffic according to customized rules so that application servers are not overwhelmed.

Traditionally, hardware load balancers and application servers are deployed in on-premises data centers and the number of load balancers depends on the expected amount of peak traffic. Load balancers are usually deployed in pairs in case one fails.

How does a Hardware Load Balancer Work?

A hardware load balancer sits between incoming traffic and internal servers, essentially acting as a “traffic cop.” When clients visit the website, they are sent first to the load balancer, which then directs clients to different servers. Most enterprises also deploy load balancers and servers in multiple locations, a procedure known as global server load balancing (GSLB). GSLB not only provides optimized response times, but also ensures high availability in disaster recovery situations. If one data center fails, GSLB systems can redirect network traffic to other available sites, minimizing the impact on end-users.

Hardware Load Balancers vs. Software Load Balancers?

The most obvious difference between hardware vs. software load balancers is that hardware load balancers require proprietary, rack-and-stack hardware appliances, while software load balancers are simply installed on standard x86 servers or virtual machines. Network load balancer hardware is typically over provisioned — in other words, they are sized to be able to handle occasional peak traffic loads. In addition, each hardware device must be paired with an additional device for high availability in case the other load balancer fails.

Another critical difference between hardware and software load balancers lies in the ability to scale. As network traffic grows, data centers must provision enough load balancers to meet peak demand. For many enterprises, this means that most load balancers stay idle until peak traffic times (e.g. Black Friday).

If traffic volumes unexpectedly exceed capacity, end-user experiences are significantly impacted. On the other hand, software load balancers are able to scale elastically to meet demand. Whether network traffic is low or high, software load balancers can simply autoscale in real time, eliminating over-provisioning costs and worries about unexpected traffic surges.

In addition, hardware load balancer configuration can be complex. Software load balancers architected on software-defined principles cross multiple data centers and hybrid-/multi-cloud environments. In fact, hardware appliances are not compatible with cloud environments, whereas software load balancers are compatible with bare metal, virtual, containers, and cloud platforms.

Where does a Hardware Load Balancer Fall short?

When choosing load balancers, enterprises should keep hardware load balancer costs in mind. All hardware appliances come with standard over-provisioning requirements and the need for additional manpower to configure and maintain the devices. Moreover, enterprises that use hardware load balancers cannot take advantage of cloud computing, which lowers CapEx and OpEx costs while offering higher performance, automation, and elasticity. Overall, even the best hardware load balancer will greatly increase enterprise TCO (especially when deploying global server load balancing).

Does Avi Offer a Hardware Load Balancer?

No, Avi Networks does not offer a hardware load balancer. However, for customers who prefer the appliance form factor, the Avi Vantage Platform can be deployed in bare metal servers or on NFV appliances like Cisco CSP 2100 delivering the convenience of a familiar deployment model with benefits of a software-defined architecture. The Avi Vantage Platform is an intent-based L4-L7 application services platform that is deployed on bare metal servers, virtual machines, containers, public clouds, and multi-cloud environments. Instead of forcing enterprises to over provision load balancers, Avi Vantage offers on-demand, elastic autoscaling that matches real-time traffic. Unlike most hardware load balancers that essentially act as black boxes, Avi also delivers unparalleled end-to-end visibility, reducing troubleshooting time to minutes.

For more information on hardware load balancers see the following resources: