Software load balancers and load balancing appliances have become indispensable components within a healthy application infrastructure. Scalability, security, observability, and reliability are more critical than ever as companies push harder towards 99.999% availability. Accordingly, traffic management is key to protecting servers and ensuring uptime.
Vendors have offered load balancers in different form factors to serve evolving infrastructure needs. Unfortunately, these solutions aren't always optimized for their intended use cases—nor do they repackage effectively into other form factors. These shortcomings make modernization more challenging and complicate mixed environment deployments.
We'll take a look at some core differences between software load balancers and load balancing appliances, and explain how HAProxy’s unique approach to building a dedicated, software-first load balancer helps users address common pain points when selecting the right form factor.
What are software load balancers?
"Pure" software load balancers are applications made to run on top of an underlying operating system. Some software load balancers come packaged with specific distributions (such as Ubuntu, Debian, or CentOS), while others ship as supplemental add-ons for web servers, firewalls, and network interfaces (such as Microsoft NLB). Many software load balancers are also open source.
Detached from an OS, software load balancers can deploy anywhere, scale horizontally with streamlined procurement, leverage whatever compute power is available to them, and keep upfront costs low. Skilled teams can take advantage of their flexibility and deep configurability to get the best performance and the perfect fit for their environment.
However, performance can be limited if sufficient capacity is not available, operational costs can rise proportionately with scaling out, and the skill requirements can be higher than some IT generalists are comfortable with, requiring knowledge of server/container management and networking.
What are load balancing appliances?
First, the term "load balancing appliance" is somewhat of a misnomer. Despite the usual association of the word “appliance” with hardware, load balancing appliances can be either hardware or virtual. In any case, appliances come with a pre-packaged OS, user interface and API, network stack, templates for integrations, plus other useful components. They're typically ready to use apart from minimal initial setup requirements.
Hardware appliances are rack-mounted devices with standardized or specialized internal components—such as optimized CPUs and advanced chipsets like Intel's QAT accelerators. These provide precisely tuneable and predictable performance. However, even virtualized workloads (discussed next) running on commercial off-the-shelf servers and cloud servers can leverage those components.
Virtual load balancing appliances are pre-built virtual machines (VMs) paired with a specific hypervisor (such as KVM, Hyper-V, and VMWare ESX). Virtual appliances come with their own OS. They often share licensing requirements with their hardware counterparts. Plus, virtual appliances can offer nearly complete feature parity with hardware appliances while providing more flexibility in deployment and pricing models.
However, cost savings and scalability can be limited in comparison with software load balancers. Getting up and running is expensive if you have to purchase specialized hardware, and prices reflect the efforts necessary to build proprietary appliances. Scaling depends on rack space, power, throughput, and concurrent connection requirements. Once connection limits (SSL/TLS included) are reached, you typically need to upgrade your appliances or buy more licenses to keep up.
Why is choosing the right load balancer form factor challenging?
Two main load balancing options lie before us: software or appliance (hardware or virtual). For those wanting the utmost flexibility, scalability, and efficiency in modern application delivery architectures, software load balancing seems like the best choice. However, organizations often face obstacles to adopting a software load balancer. Two challenges often surface:
Disappointing experiences with low-performing virtual appliances (particularly those converted from hardware appliances) sometimes shape perceptions of what’s possible with software load balancers, which can be incredibly fast.
Inconsistencies between software and appliance load balancers add friction to migrations and management overhead when running mixed deployments. Teams accustomed to load balancing appliances sometimes have a hard time adapting to "pure software plus OS" load balancers.
Consequently, many organizations are constrained by infrastructure that poorly fits their goals. HAProxy's unique approach to load balancing side-steps these obstacles to help teams build high-performing solutions they actually want.
Solving challenge #1: maximizing performance from software load balancers
Based on poor performance outcomes with virtual appliances, some organizations are reluctant to adopt true software load balancers. This concern that software load balancers won't perform well often starts with vendors, who convert their hardware appliances into virtual load balancers that don't fully leverage underlying computing power and infrastructure.
Other vendors adapt one core function (like a web server) into another with mixed results. This leads to performance issues and may cause organizations to avoid software load balancers altogether. The lines separating virtual load balancers and software load balancers have become blurred, adding to the confusion over which solution works best in a given scenario.
HAProxy solves this problem by being a software load balancer, first and foremost. In fact, we're the world's fastest and most widely used software load balancer! This avoids the common appliance-to-software conversion issue that introduces performance compromises, and equally benefits our load balancing appliances that are based on our high-performing software load balancer. Here's what a HAProxy customer had to say:
HAProxy delivers dedicated load balancing functionality that's designed to do one job incredibly well—handling upwards of 5 billion daily requests for DoubleVerify, supporting over 2 million HTTPS requests per second on one Amazon Graviton2 instance, and delivering lower latency than alternatives.
HAProxy takes full advantage of underlying computing power and infrastructure. We can squeeze maximum performance from available CPU and memory through caching and multithreading. HAProxy’s fast SSL/TLS performance is highly efficient on a 2-core server and scales up appropriately when running on powerful Intel QAT processors with TLS acceleration. Meanwhile, features like compression and traffic shaping reduce network bandwidth consumption. But that's just a snapshot of what our load balancing products offer. Check out our HAProxy Enterprise datasheet to dive even deeper.
Solving challenge #2: reducing friction of migrations and mixed deployments
It's reasonable to assume that a vendor-controlled ecosystem means greater consistency and product integration, but this isn't always the case. A common pain point is discovering that software load balancers and load balancing appliances function completely differently even when they come from the same supplier.
Capabilities, configurations, interfaces, automations, and monitoring approaches vary and therefore introduce complexity. Clashing code bases and design requirements for each form factor can result in very different products, undermining the effectiveness of these offerings and the overall vendor ecosystem. And what if you need to manage a mix of software and appliance-based load balancers, or migrate from one form factor to another? The added uncertainty that comes with vendor fragmentation can make these processes more trouble than they're worth—discouraging organizations from innovating and adopting the form factor that's right for them.
HAProxy addresses this issue by providing consistent features, configuration options, and APIs, whether you're using HAProxy Enterprise (a software load balancer), HAProxy ALOHA (a load balancer appliance), or a combination of both. Because HAProxy solutions share similar design principles and the same core codebase, organizations are free to migrate, modernize, and innovate without worrying about major inconsistencies.
This is ideal for mixed environments where HAProxy Enterprise instances operate alongside HAProxy ALOHA appliances. For example, we might place HAProxy ALOHA in front of HAProxy Enterprise to provide scalability through Layer 4 load balancing and protection against various types of volumetric attacks.
Then there's migration. HAProxy asks you to convert your old configurations (like iRules or Content Switching Policies, for example) over to a unified HAProxy configuration just once, helping you get up and running more quickly. These conversions are straightforward and result in human-readable configurations that are less verbose. Future configuration changes are therefore easier to make. This simplicity also eases the transition from HAProxy ALOHA appliances to HAProxy Enterprise instances, if that becomes necessary later. Forget about changing multiple network settings or following complex transition processes.
HAProxy removes the obstacles between you and your ideal load balancing form factor
Whether you're looking for a software load balancer, an appliance, or both, HAProxy has you covered. Our software-first approach negates many common challenges that organizations face around performance and management overhead. This means users can choose the right form factor for their infrastructure and application stack without worrying about performance or the pain of switching form factor later on.
The question isn't whether software load balancers or appliances are better. We give you the power to choose the solution that works best for you, without the usual compromises. To learn more about the benefits of performance and flexibility, check out our blog post.
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