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Load balancers, once almost exclusive to the realm of hardware devices, can now be implemented effectively in software on another server. The line between hardware and software load balancers is fading fast.
The principle difference between a hardware versus software load balancer lies in the available capacity and the amount of labor you'll invest in the platform. Hardware load balancers support a range of throughput, server counts, connectivity options and feature sets right out of the box. A hardware load balancer is often designed with efficient application-specific integrated circuits to accelerate data handling with minimum effect on a central processor. For example, the low-end Barracuda Load Balancer ADC 240 supports 10 servers with throughput up to 100 megabits per second, while the high-end ADC 840 handles up to 500 physical servers with throughput to 10 gigabits per second (Gbps) with varied copper and fiber connectivity options.
So, the question isn’t whether a hardware versus software load-balancer is better, but which method offers the capacity, feature set and support that your enterprise needs in the data center.
Organizations that prefer a software load balancer deployment, sometimes called application delivery controller or ADC, can opt for virtual appliances --prepackaged VMs. The ADCs offer many of the same features found in the hardware load balancers, though lack certain features, such as Active Directory and Kerberos authentication integration, hardware-based secure socket layer offloading and SSL hardware acceleration. Connectivity will depend on the server used to host the virtual appliance.
The Barracuda Load Balancer ADC Vx family, for example, includes a low-end Vx 340 that supports 35 real servers with up to 1 Gbps throughput, while the high-end Vx 640 supports up to 250 physical servers with up to 5 Gbps throughput. Other software load-balancer products include NGINX Plus, ZVA64 EE 4000 Virtual Appliance from Sofintel IT Engineering and open source offerings like BalanceNG V3, HAProxy 1.6.
Hardware vs. software load balancer
Hardware load balancers rely on firmware to supply the internal code base -- the program -- that operates the balancer. Hardware balancers include a management provision to update firmware as new versions, patches and bug fixes become available. Although firmware updates are usually downloadable, the actual firmware patch process is often more involved than common operating system or application file patches. Load balancers with security capabilities can update application security features such as firewalls, or some malware protection.
Software load balancers could be sensitive to OS versions, and virtual appliance deployments could experience hypervisor dependencies. If you select the software load balancing route, ensure that any OS changes or updates don't adversely affect the software load balancer. For example, platforms updates or patches can still disrupt a virtual appliance that supports VMware ESX/ESXi, Citrix XenServer, Microsoft Hyper-V, Oracle VirtualBox and other hypervisors. Conduct advanced testing to avoid the possibility of any server load-balancer disruption that OS or hypervisor dependencies can cause.
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