VMware ESX vs ESXi

Both ESX and ESXi hypervisors use the same vmkernel, so the underlying core infrastructure is the same. Although there are differences in how ESXi is managed from ESX. The differences between ESX and ESXi are narrowing with the new release of vSphere 4.1, putting both hypervisors at an equivalent level to each other.

With ESX the virtualization kernel (vmkernel) works in conjunction with the service console. The service console provides a management interface for ESX. This architecture allows administrators to log into the Service Console to run various scripts and commands for configuration and diagnostics.

VMware ESXi uses a smaller footprint, requiring 32MB of disk on the Host, allowing for faster boot times than ESX. ESXi does not include the Service Console, all the VMware agents run directly on the vmkernel. ESXi allows 3rd party modules to run in vmkernel only if they have been digitally signed by VMware, providing improved security. ESXi is a free product which can be downloaded from VMware’s web site. To utilize all the features of ESXi a license for the management console vCenter must be purchased.

ESXi can be installed to disk, or as the Embedded Edition typically sold by hardware vendors. ESXi allows for both disk and disk-less Host servers, providing increased flexibility and lower hardware and power/cooling costs when using diskless servers. There are two variations of ESXi, VMware ESXi Installable and VMware ESXi Embedded Edition. ESXi can be upgraded to a commercial version.

ESXi Features

In future releases of vSphere VMware will only provide ESXi. Existing ESX hosts will need to be migrated to ESXi to stay current with the latest hypervisor code base. The differences between ESX and ESXi are becoming so minor that it’s more an issue of getting used to managing the hypervisor slightly differently than in the past. Just as the Windows operating system has evolved, so is VMware’s hypervisor evolving.

vSphere 4.1, ESXi now supports booting from a SAN, scriptable installations and Active Directory. Management of ESXi is complemented with the full Tech Support Mode and enhancements to the Direct Console User Interface. Improvements to vSphere’s Command-Line Interface and the Management Assistant provide an alternate method to using the older ESX service console. PowerCLI can be used to automate administration tasks, such as configuration and deployment.

Upgrading ESXi

Upgrades to newer versions of ESXi have an advantage over using ESX, since a single image file is used for the ESXi upgrade. There are no issues with patches or the order or dependency of patches with ESXi. Reverting back to a previous ESXi version is much easier than with ESX since old versions are automatically saved in a backup partion.

SAN Choices

Regardless of whether you use ESX or ESXi, using a SAN (Storage Area Network) will let you take advantage of the full range of VMware’s advanced features such as vMotion, HA, DRS and DPM. The decision whether to use a FC (Fiber Channel) or an iSCSI SAN is becoming easier to make now that iSCSI performance can be proven to be more than enough for most SMB customers, and in some cases can even be faster than FC. There are many factors that affect SAN performance from the storage controllers in the SAN to the number and speed of the disks to the actual SAN fabric and Adapters in the servers.


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