ESXi: What it is and why it’s useful

The native hy­per­vi­sor ESXi doesn’t need its own a general-purpose operating system and is thus very efficient with space and resources. ESXi is mostly used for vir­tu­al­iz­ing servers.

VMware’s ESXi is a type 1 hy­per­vi­sor, also known as a bare metal hy­per­vi­sor, that’s installed directly on a physical server and can be used in­de­pen­dent­ly of any operating system. The software vSphere is used for ad­min­is­tra­tion. ESXi is based on the VMkernel and doesn’t need its own un­der­ly­ing operating system, meaning that it uses sig­nif­i­cant­ly less space than other hy­per­vi­sors. VMware launched ESXi in 2001 and still offers it today. ESXi stands for “Elastic Sky X in­te­grat­ed”.

Hy­per­vi­sors are the layer between a purely virtual machine and the physical system it runs on. The software makes it possible to manage the virtual and the physical com­po­nents involved, allocates tasks and storage space, and ensures that different machines can run on the same system without getting in each other’s way. Hy­per­vi­sors are divided into two types: type 1 hy­per­vi­sors, which aren’t connected to the host’s operating system, and type 2 hy­per­vi­sors, which require an existing operating system. ESXi is a type 1 hy­per­vi­sor.

ESX was the pre­de­ces­sor to VMware’s ESXi and was also a type 1 hy­per­vi­sor. Unlike ESXi, ESX had its own service console. That means that it used sig­nif­i­cant­ly more storage space than ESXi. ESX has been out of use since version 5.0 of vSphere, due to the sig­nif­i­cant ad­van­tages of ESXi in terms of in­stal­la­tion and storage space.

ESXi is es­pe­cial­ly popular when it comes to the vir­tu­al­iza­tion of servers and boasts excellent results in this regard. With simple hor­i­zon­tal and vertical scal­a­bil­i­ty, ESXi not only provides optimal options for par­ti­tion­ing but also enables you to work securely on one or more machines. It’s also used for (tem­porar­i­ly) separate servers and virtual test en­vi­ron­ments.

ESXi comes with a number of ad­van­tages, es­pe­cial­ly compared with its pre­de­ces­sor ESX, which used sig­nif­i­cant­ly more memory. Vir­tu­al­iz­ing entire data centers can save money, resources, and space without com­pro­mis­ing on re­li­a­bil­i­ty and security. Thanks to its proximity to hardware, ESXi boasts strong per­for­mance and makes optimal use of available resources. Man­age­ment is cen­tral­ized in the hy­per­vi­sor and the vir­tu­al­ized systems can be easily exported. A high level of flex­i­bil­i­ty and quick in­stal­la­tion are ad­di­tion­al ad­van­tages. If your ESXi server is rented, you’ll save even more money. And as mentioned above, you’ll have numerous options for scaling.

The software vSphere is used for managing ESXi and is available in both free and paid versions. With the com­plete­ly free version VMware vSphere Hy­per­vi­sor, you won’t be able to com­mu­ni­cate with vCenter servers and can only manage each host in­di­vid­u­al­ly. The paid versions all differ in price and their range of features. The maximum number of servers will also vary based on which pricing plan you choose.

There are a number of free and paid al­ter­na­tives to ESXi. One of the most popular open source solutions is Citrix XenServer, which is not only free but also rel­a­tive­ly easy to use. However, compared with com­mer­cial offerings, the range of features is rather limited. The same is true of Proxmox VE and KVM. Hyper-V by Microsoft is available for Windows servers and client operating systems. Like ESXi/vSphere, this hy­per­vi­sor is available in different price models.