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What are the 10 major differences between VMware ESX

Server and ESXi Server?

1. VMware ESXi Server has no service console 

The traditional (full) ESX Server has a special built-in virtual machine called the ³serviceconsole´. This service console is really a modified version of Red Hat Enterprise Linux thatis installed and running in every ESX Server by default. The service console has specialaccess to the VMware-proprietary VMFS file system. 3rd party applications can be installedin the service console and Linux-based utilities can be run in the service console.Additionally, VMware includes a number of ESX-related tools in the service console, most of which start with ³esxcfg-³ and they are run by accessing the service console with SSH.

As VMware ESXi Server has no service console, there is no SSH access to the server and

there are no 3rd party applications that can be installed on the server. However, there are also benefits to NOT having these features (discussed more below).

2. VMware ESXi Server uses RCLI instead of service console utilities  

As ESXi doesn¶t have any CLI with VMware-related or Linux utilities, VMware needed to provide a CLI interface to ESXi. What VMware came up with is the Remote Command lineInterface (RCLI). This is an application that you typically install as a VM and it is used to

 perform scheduled or ad hock scripting on the VMware Infrastructure. The ESXi RCLI is itsown command line where ESX server service console scripting would be made up of mostlyLinux utilities.

For more information on how to manage ESXi, take a look at Managing VMware ESXi.

3. VMware ESXi Server is extremely thin = fast installation + faster boot 

Because the service console has been removed from ESXi, the footprint in memory has beenreduced to just 32MB. In my opinion, it is truly amazing that you can run a hypervisor,allowing you to run virtual machines on your server, with just 32MB of RAM overhead. Incomparison, the full ESX Server on disk footprint is about 2GB.

Because the hypervisor is so small, the installation happens in about 10 minutes (or so) andthe server boots up in 1-2 minutes. This is quite different from the full ESX server installationand boot, both of which are longer.

4. VMware ESXi Server can be purchased as an embedded hypervisor on hardware  

While ESXi is so small that it can be easily installed and can even be booted from a USBFlash disk, what is truly unique about ESXi is that it is being sold by hardware vendors as a

 built-in hypervisor. That means that, say, you buy a Dell server, ESXi can be built inside theserver (embedded) on a flash chip, on the motherboard. There is no installation of ESXi ondisk.

5. VMware ESXi Server¶s service console (firewall) is configured differently

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As there is no service console to protect with the ESX Server security profile (softwarefirewall), the security profile configuration in ESXi is very simplistic. The ESXi security

 profile configuration consists of a couple of services that you can either enable or not enablewith inbound access. Here is a comparison between the two:

Figure 1: ESXi Security Profile ± only 2 services

Figure 2: VMware ESX Server (full) Security Profile

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For more information on how to configure VMware ESX Server Security Profiles ± see myVirtualizationAdmin.com article How to schedule tasks with the VMware Infrastructure

Client and ESX Server. 

6. VMware ESXi Server has a ³yellow firmware console´ 

Instead of the full ESX Server ³service console´ boot (which looks like a Linux server  booting), ESXi has a tiny ³Direct Console User Interface (DCUI)´. Unofficially, I like to callthis the ³yellow firmware console´. In this ESXi console, all that you can configure are somevery basic ESXi server options such as the root user password, network settings, and a coupleother items. In the graphic below, you can see why I call it ³yellow´:

Figure 3: ESXi yellow firmware console / DCUI

Because this tiny firmware console (did I mention that it¶s yellow?) has so few features, theserver is virtually ³stateless´. A new server can be configured in seconds because there isalmost nothing to configure.

7. VMware ESXi Server has server health status built in  

With ESXi some hardware monitoring features are built into the hypervisor. With ESXServer, this is not yet built in. Instead, you must install hardware monitoring software in theservice console. For more information on ESXi server health status and how to installvendor-specific utilities to provide similar information on ESX Servers, please see my article:

Obtaining server health status in VMware ESX and VMware ESXi.

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 Figure 4: ESXi Health Status

8. Some networking features are configured through the service console are not

available or are experimental 

As ESXi is relatively new and as ESX server has the option to install code for advanced ESXServer features, not all features available in the full ESX Server are also available in ESXi. Infact, I have had issues getting VMware High Availability (VMHA) to work in ESXi. VMHAwas not officially supported on ESXi until some recent patches came out for ESXi. Still, evenafter the patches, I had difficulties with ESXi and VMHA.

There are other ESX Server features that are ³experimental´ on ESXi. For the full list visit:Differences in Supported Networking Features Between ESX Server 3.5 and ESX Server 3i 

9. VMware ESXi Server requires fewer patches and less rebooting  

Because the full ESX server essentially has a modified Linux system as the service console,there are many patches that have to be deployed to keep it secure. With ESXi, on the

contrary, the server has very few patches that need to be applied. Because ESXi has noservice console and it is considered more secure and more reliable. Security, Reliability, andMaintainability, are all major factor when considering a hypervisor.

10. You can buy VMware ESXi Server for as little as $495 

With the full version of ESX Server, the least expensive purchase option is the Foundation(Starter) kit for about $1,500, while you can purchase ESXi only (with no support) for $495.On the other hand, if you do get the Foundation kit, you not only get the full ESX Server but

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also ESXi and a number of VMware Infrastructure Suite options. Still, obtaining ESXi for under $500 allows a server to do so much more than it ever could before.

Which version of VMware ESX Server is best for you?

I am not here to sell you on VMware, on ESX Server, or ESXi Server, what I am here to do isto inform you of the drastic differences between these two versions of ³ESX Server´. In my

opinion, ESX Server (full) must be used if you have 3rd party apps or if you just want to haveaccess to the ³Linux-style´ service console.

On the other hand, if you are willing to give up those two benefits, with ESXi, you will get anESXi Server that boots faster, has fewer patches to deploy, and is more reliable. ESXi is alsothe least expensive option.

I recommend testing both VMware ESX Server and ESXi server. Both are available for a freeevaluation download from VMware Inc.

ESXi and ESX Architectures Compared

VMware ESX Architecture. In the original ESX architecture, the virtualization kernel (referred to as the

vmkernel) is augmented with a management partition known as the console operating system (also known as

COS or service console). The primary purpose of the Console OS is to provide a management interface into the

host. Various VMware management agents are deployed in the Console OS, along with other infrastructure

service agents (e.g. name service, time service, logging, etc). In this architecture, many customers deploy other 

agents from 3rd parties to provide particular functionality, such as hardware monitoring and system management.

Furthermore, individual admin users log into the Console OS to run configuration and diagnostic commands and

scripts.

VMware ESXi Architecture. In the ESXi architecture, the Console OS has been removed and all of the VMware

agents run directly on the vmkernel. Infrastructure services are provided natively through modules included with

the vmkernel. Other authorized 3rd party modules , such as hardware drivers and hardware monitoring

components, can run in vmkernel as well. Only modules that have been digitally signed by VMware are allowed

on the system, creating a tightly locked-down architecture. Preventing arbitrary code from running on the ESXi

host greatly improves the security of the system.

Architectures Compared

VMware ESX [~ 2 GB] VMware ESXi [< 100 MB]

y  VMware agents run in Console OS y  VMware agents ported to run directly on

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VMware ESX [~ 2 GB] VMware ESXi [< 100 MB]

y  Nearly all other management functionalityprovided by agents running in the Console OS

y  Users must log into Console OS in order to runcommands for configuration and diagnostics

VMkernel

y   Authorized 3rd party modules can also run inVmkernel. These provide specific functionality

o  Hardware monitoring

o

  Hardware drivers

y  VMware components and third partycomponents can be updated independently

y  The ³dual-image´ approach lets you revert toprior image if desired

y  Other capabilities necessary for integration intoan enterprise datacenter are provided natively

y  No other arbitrary code is allowed on thesystem

Understand the Difference between ESX and ESXi

VMware ESXi is VMware¶s next-generation hypervisor architecture. Learn about the differences with the previous

generation architecture, VMware ESX:

Capability ESX 4.0 ESX 4.1 ESXi 4.0 ESXi 4.1

Service Console  Present Present Removed Removed

Admin/config CLIs COS + vCLI COS + vCLI PowerCLI+ vCLI

PowerCLI+ vCLI

AdvancedTroubleshooting 

COS COS TechSupportMode

TechSupportMode

Scripted Installation Supported Supported NotSupported

Supported

Boot from SAN  Supported Supported NotSupported

Supported

SNMP  Supported Supported Supported(limited)

Supported(limited)

Active Directory  3rd party in COS Integrated NotSupported

Integrated

HW Monitoring  3rd party agents in COS 3rd party agents inCOS

CIMproviders

CIMproviders

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Web Access  Supported Not Supported NotSupported

NotSupported

Serial Port Connectivity  Supported Supported NotSupported

NotSupported

Jumbo Frames  Supported Supported Supported Supported

See the KB article for a detailed comparison.

Compare ESXi to Other Vendors' Offerings

Hypervisor Attributes VMware ESXi/ESX 4.1Windows Server 2008

R2 with Hyper-V

CitrixXenServer 

5.6

Small Disk Footprint

70 MB disk footprint(VMware ESXi) 

>2GB with Server Coreinstallation

~10GB with full WindowsServer installation

1.8GB

OS Independence

No reliance on general purposeoperating system(VMware ESXi) 

Relies on Windows 2008in Parent Partition

Relies onLinux in Dommanagement

Partition

Hardened Drivers

Optimized with hardwarevendors

Generic Windows drivers GenericLinux Drivers

 Advanced MemoryManagement  Ability to reclaim unused

memory, de-duplicate memorypages, compress memory

pages

No ability to reclaimunused physical memory,de-duplicate or compress

pages

Recentlyadded basicovercommit,but does not

adjustmemory

allocationbased on VM

usage; nodeduplication

or compression

of pages

Advanced StorageManagement  VMware vStorage VMFS,

Storage vMotion Lacks an integrated

cluster file system, no liveLacks anintegrated

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storage migration cluster filesystem, nolive storagemigration,

storagefeatures

support very

few arrays

High I/O Scalability

Direct driver model I/O bottleneck in parentOS

I/Obottleneck in

Dom0management

OS

Host Resource Management

Network traffic shaping, per-VMresource shares, set quality of 

service priorities for storage and

network I/O

Lacks similar capabilit ies Lacks similar capabilities

Performance Enhancements 

 AMD RVI, Intel EPT largememory pages, universal 8-wayvSMP, VMI paravirtualization,VMDirectPath I/O, PV guest

SCSI driver 

Large memory pages,4-way vSMP on Windows2008 and Windows 7 VMs

only

No largememory

pages, noparavirt

guest SCSIdevice, nodirect I/O

devicesupport

Virtual Security Technology  VMware VMsafe� security API Nothing comparable Nothing

comparable

Flexible Resource Allocation

Hot add VM vCPUs andmemory, VMFS volume grow,

hot extend virtual disks, hot addvirtual disks

Only hot add virtual disks Nothingcomparable