When to use Azure Load Balancer
Azure Load Balancer is best suited for applications that require ultra-low latency and high performance. Load Balancer is suitable for your organization's needs because you're replacing existing network hardware devices that load balance traffic across applications. The applications used multiple VM tiers when the applications were on-premises with an Azure service that has the same functionality.
Because Load Balancer operates at Layer 4 like hardware devices that were used on-premises before the organization migrated to Azure, you can use Load Balancer to replicate that hardware device functionality. This functionality includes using health probes to ensure that Load Balancer doesn't forward traffic to failed VM nodes. It also includes using session persistence to ensure that clients only communicate with a single VM during a session.
You can configure public load balancers for front-end traffic to web tiers of applications. You can also configure internal load balancers to balance traffic between the web tier and the tier that performs data analysis and transformation tasks.
You can configure inbound NAT rules to allow remote desktop protocol access to a VM instance to perform administrative tasks.
When not to use Azure Load Balancer
Azure Load Balancer isn't appropriate if you have a web application that doesn't require load balancing running on a single IaaS VM instance. For example, if your web application only receives a small amount of traffic and the existing infrastructure already competently deals with the existing load, there's no need to deploy a back-end pool of VMs and no need to use Load Balancer.
Azure provides other load-balancing solutions as alternatives to Azure Load Balancer, including Azure Front Door, Azure Traffic Manager, and Azure Application Gateway:
- Azure Front Door is an application-delivery network that provides a global load balancing and site acceleration service for web applications. It offers Layer 7 capabilities for your application like TLS/SSL offload, path-based routing, fast failover, a web application firewall, and caching to improve performance and high availability of your applications. Choose this option in scenarios such as load balancing a web app deployed across multiple Azure regions.
- Azure Traffic Manager is a DNS-based traffic load balancer that allows you to distribute traffic optimally to services across global Azure regions while providing high availability and responsiveness. Because Traffic Manager is a DNS-based load-balancing service, it load balances only at the domain level. For that reason, it can't fail over as quickly as Front Door, because of common challenges around DNS caching and systems not honoring DNS TTLs.
- Azure Application Gateway provides Application Delivery Controller (ADC) as a service, offering various Layer 7 load-balancing capabilities. Use it to optimize web farm productivity by offloading CPU-intensive TLS/SSL termination to the gateway. Application Gateway works within a region rather than globally.
- Azure Load Balancer is a high-performance, ultra-low-latency Layer 4 load-balancing service (inbound and outbound) for all UDP and TCP protocols. Its built to handle millions of requests per second while ensuring your solution is highly available. Azure Load Balancer is zone-redundant, ensuring high availability across availability zones. If Adatum had applications that required web application firewall functionality, Azure Load Balancer wouldn't be an appropriate solution for the company.