ESXi vs. ESX: A comparison of features

VMware made the decision to make VMware ESXi, our next generation hypervisor, freely available to proliferate the VMware platform and allow administrators to prove its value at no cost. However, the fact that the older platform, VMware ESX, is not also available for free has lead some people to believe that ESXi may be inferior or not as feature-rich as ESX. This is certainly not the case. In fact, the opposite is true. ESXi has a superior architecture and we encourage customers to deploy ESXi as part of any new vSphere deployment. Our future posts will compare ESX 4 and ESXi 4 in detail on topics like hardware compatibility list, performance, and management to demonstrate that ESXi is either on par with or superior than ESX. But for now, here are some key points you should know about ESXi vs. ESX:

1. The functionality and performance of VMware ESX and ESXi are the same; the difference between the two hypervisors resides in their packaging architecture and operational management. VMware ESXi is the latest hypervisor architecture from VMware. It has an ultra thin footprint with no reliance on a general-purpose OS, setting a new bar for security and reliability (learn more).
2. In the future, ESXi’s superior architecture will be the exclusive focus of VMware's development efforts.
3. New and existing customers are highly encouraged to deploy ESXi. Many Fortune 100 companies have already standardized on the ESXi platform.

Although one instance of free VMware ESXi can be managed with the vSphere Client, the free version has two important limitations:

1. vCenter cannot manage free ESXi without a vSphere license as its APIs only grant read-only access.
2. Automated scripts cannot change hypervisor settings. 

However, once ESXi is licensed for any vSphere SKU, its APIs become both read- and write-accessible, unlocking the full functionality of vCLI, vMA, PERL Took Kit, Powershell Tool Kit, or other VMware management interfaces.The table below, available here, explains how different license levels unlock ESXi (and ESX) functionality. Please note that vSphere Essentials, an all inclusive package that can be deployed on up to three servers, is priced at under $1000. 

The ESX Team

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