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What are the limitations of free ESXi?

VMware's ESXi hypervisor is free to license and use, but its capabilities are limited without vSphere. You get what you pay for.

VMware customers can use ESXi to build powerful virtualization platforms, but the hypervisor without vCenter and the vSphere client has serious shortcomings that make it better suited for small organizations than an enterprise.

Naturally, software you pay for offers more. In this case, free ESXi lacks tools and features such as vMotion, Fault Tolerance and vSAN, all of which require a minimum of three nodes to run. The limitations of free ESXi fall into two categories: hardware and functionality.

Difference between ESXi and vSphere

The terms ESXi and vSphere are sometimes used interchangeably, but it's important to understand the difference when you compare free and supported versions. ESXi is a type-1 hypervisor available for free download. Customers have the option to purchase commercial support and software, called vCenter, to help manage multiple ESXi installations. VMware vSphere is the name of a software bundle that includes the free ESXi hypervisor, vCenter and the vSphere management client. VMware offers a variety of licensing options for vSphere for companies that need advanced features and professional support.

Free ESXi limitations

VMware has tried to eliminate the physical restrictions from the free ESXi hypervisor. For example, the memory limitation in ESXi 5 was set to 32 GB. The most current version of ESXi (6.7) has no hardware limitations other than a maximum of two physical CPUs and eight vCPUs per VM. There is no problem using two hex core Xeon processors, 128 GB RAM and a redundant array of independent disks set up on a single machine. Such a machine would be a potent virtualization host, even without any additional licensing.

Most large production environments only use two socket hosts due to the significant cost per socket under the Enterprise license, so it makes the most sense to increase the core count and reduce physical sockets. This also explains why manufacturers began to license per core, rather than per socket.

A server that uses free ESXi can support a large number of VMs. You might notice during day-to-day operations that you can't cluster servers or perform a storage vMotion while servers are still active. You can still move VMs between data stores, but it's a more complex process and requires downtime.

Be aware of deal breakers in free ESXi

Built-in monitoring is another feature absent from the free edition of ESXi. This can be an issue, depending on your environment.

This last item might be a deal breaker for some: The free version of ESXi does not offer Active Directory integration. Customers can still have their own account to log in with -- which provides a degree of attribution -- they just need to add users directly to the host.

I've noticed in smaller commercial enterprise spaces that designs from some providers use multiple dual redundant VMs; one on each host. Load-balancing logic is built into self-healing applications. You can avoid the cost of a more expensive license by keeping two copies of the same data on different hosts.

There are many ways you can leverage the free ESXi to provide useful system setups. More advanced licenses provide more features and functionality, but a free license offers a suitable level of performance and utility in many cases.

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