VMware ESX explained

VMware ESXi
Developer:VMware (Broadcom)
Latest Release Version:8.0 Update 3g (Build 24859861)[1]
Latest Release Date:[2]
Platform:IA-32 (x86-32) (discontinued in 4.0 onwards),[3] x86-64, ARM[4]
Genre:Native hypervisor (type 1)
License:Proprietary

VMware ESX (formerly named ESXi) and a different historic VMware ESX [5] are enterprise-class, type-1 hypervisors developed by VMware, now a subsidiary of Broadcom, for deploying and serving virtual computers. As type-1 hypervisors, ESX is not a software application that is installed on an operating system (OS); instead, they include and integrate vital OS components, such as a kernel.[6]

Prior to ESXi 3.0 (released in 2008) there was only the original hypervisor named ESX, and for a while both hypervisor products existed (until the final 4.1 release of the historic ESX in 2010). ESXi replaces the Service Console (a rudimentary operating system) with a more closely integrated OS. ESX/ESXi is the primary component in the VMware Infrastructure software suite.[7] However from version 9.0, VMware renamed ESXi to ESX despite the name having already been used before for their earlier hypervisor product.[8]

The name ESX originated as an abbreviation of Elastic Sky X.[9] [10] In September 2004, the replacement for ESX was internally called VMvisor, but later changed to ESXi (as the "i" in ESXi stood for "integrated").[11] [12]

Architecture

ESX runs on bare metal (without running an operating system)[13] unlike other VMware products.[14] It includes its own kernel. In the historic VMware ESX, a Linux kernel was started first[15] and then used to load a variety of specialized virtualization components, including ESX, which is otherwise known as the vmkernel component.[16] The Linux kernel was the primary virtual machine; it was invoked by the service console. At normal run-time, the vmkernel was running on the bare computer, and the Linux-based service console ran as the first virtual machine. VMware dropped development of historic ESX at version 4.1, and now exclusively uses ESXi (since renamed to ESX in 2025), which does not include a Linux kernel at all.[17]

The vmkernel is a microkernel[18] with three interfaces: hardware, guest systems, and the service console (Console OS).

Interface to hardware

The vmkernel handles CPU and memory directly, using scan-before-execution (SBE) to handle special or privileged CPU instructions[19] [20] and the SRAT (system resource allocation table) to track allocated memory.[21]

Access to other hardware (such as network or storage devices) takes place using modules. At least some of the modules derive from modules used in the Linux kernel. To access these modules, an additional module called vmklinux implements the Linux module interface. According to the README file, "This module contains the Linux emulation layer used by the vmkernel."[22]

The vmkernel uses the device drivers:[22]

  1. net/e100
  2. net/e1000
  3. net/e1000e
  4. net/bnx2
  5. net/tg3
    1. net/pcnet32
    2. scsi/adp94xx
  6. scsi/aic7xxx
  7. scsi/aic79xx
  8. scsi/ips
  9. scsi/lpfcdd-v732
  10. scsi/megaraid2
  11. scsi/mptscsi_2xx
  12. scsi/qla2200-v7.07
  13. scsi/megaraid_sas
  14. scsi/qla4010
  15. scsi/qla4022
    1. scsi/aacraid_esx30
  16. scsi/lpfcdd-v7xx
  17. scsi/qla2200-v7xx

These drivers mostly equate to those described in VMware's hardware compatibility list.[23] All these modules fall under the GPL. Programmers have adapted them to run with the vmkernel: VMware Inc. has changed the module-loading and some other minor things.[22]

Service console

In the historic ESX, the Service Console is a vestigial general purpose operating system most significantly used as bootstrap for the VMware kernel, vmkernel, and secondarily used as a management interface. Both of these Console Operating System functions were deprecated since historic ESX development stopped at version 4.1 and so the next version of 5.0 was ESXi only.[24] The Service Console, for all intents and purposes, is the operating system used to interact with VMware ESX and the virtual machines that run on the server.

Purple Screen of Death

In the event of a hardware error, the vmkernel can catch a Machine Check Exception.[25] This results in an error message displayed on a purple diagnostic screen. This is colloquially known as a purple diagnostic screen, or purple screen of death (PSoD, confer blue screen of death (BSoD)).

Upon displaying a purple diagnostic screen, the vmkernel writes debug information to the core dump partition. This information, together with the error codes displayed on the purple diagnostic screen can be used by VMware support to determine the cause of the problem.

Versions

VMware ESX used to be available in two main types: ESX (version 4.1 and earlier) and ESXi (version 3.5 onwards), but as of version 5, the original ESX has been discontinued in favor of ESXi (since renamed to ESX from version 9.0 onwards).

Historic ESX and ESXi before version 5.0 do not support Windows 8/Windows 2012. These Microsoft operating systems can only run on ESXi 5.x or later.[26]

VMware ESX (formerly ESXi) is a smaller-footprint version of ESX which does not include the ESX Service Console nor use a Linux Kernel. Before Broadcom acquired VMware, it was available - without the need to purchase a vCenter license - as a free download from VMware, with some features disabled.[27] [28] [29]

ESXi stood for "ESX integrated".[30]

VMware ESX (formerly ESXi) originated as a compact version of VMware ESX (historic) that allowed for a smaller 32 MB disk footprint on the host. With a simple configuration console for mostly network configuration and remote based VMware Infrastructure Client Interface, this allows for more resources to be dedicated to the guest environments.

Two variations of ESX exist:

The same media can be used to install either of these variations depending on the size of the target media.[31] One can upgrade ESXi to VMware Infrastructure 3[32] or to VMware vSphere 4.0 ESXi.

ESXi was originally named VMware ESX Server ESXi edition, through several revisions the ESXi product finally became VMware ESXi 3. New editions then followed: ESXi 3.5 up to ESXi 8, before being renamed to ESX with version 9.

GPL violation lawsuit

VMware has been sued by Christoph Hellwig, a Linux kernel developer. The lawsuit began on March 5, 2015. It was alleged that VMware had misappropriated portions of the Linux kernel,[33] [34] and, following a dismissal by the court in 2016, Hellwig announced he would file an appeal.[35]

The appeal was decided February 2019 and again dismissed by the German court, on the basis of not meeting "procedural requirements for the burden of proof of the plaintiff".[36]

In the last stage of the lawsuit in March 2019, the Hamburg Higher Regional Court also rejected the claim on procedural grounds. Following this, VMware officially announced that they would remove the code in question.[37] This followed with Hellwig withdrawing his case, and withholding further legal action.[38]

Related or additional products

The following products operate in conjunction with ESX:

Cisco Nexus 1000v

Network-connectivity between ESX hosts and the VMs running on it relies on virtual NICs (inside the VM) and virtual switches. The latter exists in two versions: the 'standard' vSwitch allowing several VMs on a single ESX host to share a physical NIC and the 'distributed vSwitch' where the on different ESX hosts together form one logical switch. Cisco offers in their Cisco Nexus product-line the Nexus 1000v, an advanced version of the standard distributed vSwitch. A Nexus 1000v consists of two parts: a supervisor module (VSM) and on each ESX host a virtual Ethernet module (VEM). The VSM runs as a virtual appliance within the ESX cluster or on dedicated hardware (Nexus 1010 series) and the VEM runs as a module on each host and replaces a standard dvS (distributed virtual switch) from VMware.

Configuration of the switch is done on the VSM using the standard NX-OS CLI. It offers capabilities to create standard port-profiles which can then be assigned to virtual machines using vCenter.

There are several differences between the standard dvS and the N1000v; one is that the Cisco switch generally has full support for network technologies such as LACP link aggregation or that the VMware switch supports new features such as routing based on physical NIC load. However, the main difference lies in the architecture: Nexus 1000v is working in the same way as a physical Ethernet switch does while dvS is relying on information from ESX. This has consequences for example in scalability where the Kappa limit for a N1000v is 2048 virtual ports against 60000 for a dvS.

The Nexus1000v is developed in co-operation between Cisco and VMware and uses the API of the dvS.[43]

Third-party management tools

Because VMware ESX is a leader in the server-virtualization market,[44] software and hardware vendors offer a range of tools to integrate their products or services with ESX. Examples are the products from Veeam Software with backup and management applications[45] and a plugin to monitor and manage ESX using HP OpenView,[46] Quest Software with a range of management and backup-applications and most major backup-solution providers have plugins or modules for ESX. Using Microsoft Operations Manager (SCOM) 2007/2012 with a Bridgeways ESX management pack gives the user a realtime ESX datacenter health view.

Hardware vendors such as Hewlett Packard Enterprise and Dell include tools to support the use of ESX(i) on their hardware platforms. An example is the ESX module for Dell's OpenManage management platform.[47]

VMware has added a Web Client[48] since v5 but it will work on vCenter only and does not contain all features.[49]

Known limitations

As of September 2020, these are the known limitations of VMware ESXi 7.0 U1.

Infrastructure limitations

Some maximums in ESXi Server 7.0 may influence the design of data centers:[50] [51]

Performance limitations

In terms of performance, virtualization imposes a cost in the additional work the CPU has to perform to virtualize the underlying hardware. Instructions that perform this extra work, and other activities that require virtualization, tend to lie in operating system calls. In an unmodified operating system, OS calls introduce the greatest portion of virtualization "overhead".

Paravirtualization or other virtualization techniques may help with these issues. VMware developed the Virtual Machine Interface for this purpose, and selected operating systems support this. A comparison between full virtualization and paravirtualization for the ESX Server[52] shows that in some cases paravirtualization is much faster.

Network limitations

When using the advanced and extended network capabilities by using the Cisco Nexus 1000v distributed virtual switch the following network-related limitations apply:[43]

Fibre Channel Fabric limitations

Regardless of the type of virtual SCSI adapter used, there are these limitations:[53]

See also

External links

Notes and References

  1. Web site: Build numbers and versions of VMware ESXi/ESX .
  2. Web site: VMware ESXi 8.0 Update 3g Release Notes.
  3. Web site: VMware ESX 4.0 only installs and runs on servers with 64bit x86 CPUs. 32bit systems are no longer supported. . VMware, Inc. . 25 December 2019 . 15 February 2017 . https://web.archive.org/web/20170215031032/http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1009080 . dead .
  4. Web site: Announcing the ESXi-ARM Fling. . VMware, Inc. .
  5. Web site: Build numbers and versions of VMware ESXi/ESX . 2025-09-20 . knowledge.broadcom.com.
  6. Web site: ESX Server Architecture . VMware . 2009-10-22 . https://web.archive.org/web/20091107080723/https://www.vmware.com/support/esx21/doc/esx21_admin_system_architecture.html . 2009-11-07.
  7. Web site: VMware:vSphere ESX and ESXi Info Center . 25 December 2019 . 14 July 2016 . https://web.archive.org/web/20160714061742/http://www.vmware.com/products/esxi-and-esx/overview.html . dead .
  8. https://vninja.net/2025/06/18/esx-to-esxi-and-back-again/ ESX to ESXi and Back Again
  9. Web site: What does ESX stand for? . 3 October 2014 . https://web.archive.org/web/20141220115744/http://vmfaq.com/index.php?View=entry&EntryID=32 . 20 December 2014 . dead . dmy-all.
  10. Web site: Glossary . 2011 . Developer's Guide to Building vApps and Virtual Appliances: VMware Studio 2.5 . . Palo Alto . 153 . 2011-11-09 . 6 February 2020 . https://web.archive.org/web/20200206223741/https://www.vmware.com/support/developer/studio/studio25/studio_developer.pdf . dead.
  11. News: Did you know VMware Elastic Sky X (ESX) was once called 'Scaleable Server'? . 2014-05-12 . UP2V . 2018-05-09 . en-US . 10 June 2019 . https://web.archive.org/web/20190610141027/http://up2v.nl/2014/05/12/did-you-know-vmware-elastic-sky-x-esx-was-once-called-scaleable-server/ . dead.
  12. News: VMware ESXi was created by a French guy !!! ESX Virtualization . 2009-09-26 . ESX Virtualization . 2018-05-09 . en-US.
  13. Web site: "ESX Server Datasheet" . 25 December 2019 . 3 May 2020 . https://web.archive.org/web/20200503014105/https://www.vmware.com/pdf/esx_datasheet.pdf . dead .
  14. Web site: ESX Server Architecture . Vmware.com . 2009-07-01 . https://web.archive.org/web/20070929084239/https://www.vmware.com/support/esx21/doc/esx21_admin_system_architecture.html . 29 September 2007.
  15. Web site: ESX machine boots . https://ghostarchive.org/varchive/youtube/20211213/AJ5yM_kdhUk . 2021-12-13 . live. Video.google.com.au . 12 June 2006 . 2009-07-01.
  16. Web site: VMKernel Scheduler. 27 May 2008. vmware.com. 2016-03-10.
  17. Web site: Mike. Foley. It's a Unix system, I know this!. VMware Blogs. VMware.
  18. Web site: Support for 64-bit Computing . Vmware.com . 19 April 2004 . 2009-07-01 . https://web.archive.org/web/20090702000340/http://www.vmware.com/company/news/releases/64bit.html . 2 July 2009 . dead . dmy-all .
  19. http://markus-gerstel.de/files/2005-Xen.pdf Gerstel, Markus: "Virtualisierungsansätze mit Schwerpunkt Xen"
  20. Web site: VMware ESX . 25 December 2019 . 21 April 2016 . https://web.archive.org/web/20160421165148/http://www.vmware.com/resources/techresources/1009 . dead .
  21. Web site: VMware ESX Server 2: NUMA Support . 2005 . VMware Inc . Palo Alto, California . 7 . 2011-03-29 . SRAT (system resource allocation table) – table that keeps track of memory allocated to a virtual machine. . 25 February 2021 . https://web.archive.org/web/20210225194824/https://www.vmware.com/pdf/esx2_NUMA.pdf . dead.
  22. Web site: ESX Server Open Source . Vmware.com . 2009-07-01.
  23. Web site: ESX Hardware Compatibility List . Vmware.com . 10 December 2008 . 2009-07-01 . 9 December 2008 . https://web.archive.org/web/20081209072153/http://www.vmware.com/resources/techresources/cat/119 . dead .
  24. Web site: ESXi vs. ESX: A comparison of features . Vmware, Inc . 2009-06-01 . 19 July 2012 . https://web.archive.org/web/20120719133736/http://blogs.vmware.com/esxi/2009/06/esxi-vs-esx-a-comparison-of-features.html . dead .
  25. Web site: "KB: Decoding Machine Check Exception (MCE) output after a purple diagnostic screen publisher=VMware, Inc." . 25 December 2019 . 15 February 2017 . https://web.archive.org/web/20170215032415/http://kb.vmware.com/kb/1005184%7Ctitle%3D . dead .
  26. VMware KBArticle Windows 8/Windows 2012 doesn't boot on ESX, visited 12 September 2012
  27. Web site: Download VMware vSphere Hypervisor (ESXi). www.vmware.com. 22 July 2014. 19 November 2018. https://web.archive.org/web/20181119125600/https://my.vmware.com/web/vmware/info/slug/datacenter_cloud_infrastructure/vmware_vsphere_hypervisor_esxi/5_5#drivers_tools. dead.
  28. Web site: Getting Started with ESXi Installable. VMware. 22 July 2014. 20 September 2019. https://web.archive.org/web/20190920181041/https://www.vmware.com/pdf/vsphere4/r41/vsp_41_esxi_i_get_start.pdf. dead.
  29. Web site: VMware ESX and ESXi 4.1 Comparison . Vmware.com . 2011-06-09 .
  30. Web site: What do ESX and ESXi stand for? . 2011-08-31 . VM.Blog. . 2016-06-21 . Apparently, the 'i' in ESXi stands for Integrated, probably coming from the fact that this version of ESX can be embedded in a small bit of flash memory on the server hardware..
  31. Web site: ESXi embedded vs. ESXi installable FAQ . Andreas Peetz . 2014-08-11.
  32. Web site: Free VMware ESXi: Bare Metal Hypervisor with Live Migration . VMware . 2009-07-01.
  33. Web site: Conservancy Announces Funding for GPL Compliance Lawsuit . sfconservancy.org . 5 March 2015 . 2015-08-27.
  34. Web site: Copyleft Compliance Projects - Software Freedom Conservancy . Sfconservancy.org . 2018-05-25 . 2020-02-07.
  35. Web site: 9 August 2016 . Hellwig To Appeal VMware Ruling After Evidentiary Set Back in Lower Court . dead . https://web.archive.org/web/20200114173909/http://bombadil.infradead.org/~hch/vmware/2016-08-09.html . January 14, 2020.
  36. Web site: Klage von Hellwig gegen VMware erneut abgewiesen. 1 March 2019.
  37. Web site: 2019-03-04 . VMware's Update to Mr. Hellwig's Legal Proceedings . deviated . https://web.archive.org/web/20210727091510/https://www.vmware.com/company/news/updates/march-2019-hellwig-legal-proceedings.html . 2021-07-27 . VMware.com .
  38. Web site: Press release . bombadil.infradead.org . 2019 . 2020-02-07 . 3 May 2020 . https://web.archive.org/web/20200503014111/http://bombadil.infradead.org/~hch/vmware/Pressrelease-2019-04-03.pdf . dead .
  39. VMware Blog by Kyle Gleed: vMotion: what's going on under the covers, 25 February 2011, visited: 2 February 2012
  40. VMware website vMotion brochure . Retrieved 3 February 2012
  41. Web site: Archived copy . www.vmware.com . 17 January 2022 . https://web.archive.org/web/20091228223853/http://www.vmware.com/files/pdf/VMware-Storage-VMotion-DS-EN.pdf . 28 December 2009 . dead.
  42. Web site: Archived copy . www.vmware.com . 17 January 2022 . https://web.archive.org/web/20101121142244/http://www.vmware.com/files/pdf/VMware-Fault-Tolerance-FT-DS-EN.pdf . 21 November 2010 . dead.
  43. Overview of the Nexus 1000v virtual switch, visited 9 July 2012
  44. http://www.crn.com/news/virtualization/232900547/vmware-continues-virtualization-market-romp.htm VMware continues virtualization market romp
  45. About Veeam, visited 9 July 2012
  46. http://www.veeam.com/vmware-esx-monitoring-hp-operations.html Veeam OpenView plugin for VMware
  47. https://en.community.dell.com/techcenter/systems-management/w/wiki/1977.openmanage-support-for-vmware-esxi-5-0.aspx OpenManage (omsa) support for ESXi 5.0
  48. VMware info about Web Client – VMware ESXi/ESX 4.1 and ESXi 5.0 Comparison
  49. Availability of vSphere Client for Linux systems – What the web client can do and what not
  50. Web site: What's New with VMware vSphere 7 Update 1 . VMware vSphere Blog . 15 September 2020 . 9 June 2023.
  51. Web site: VMware Configuration Maximum tool. 11 February 2021. 10 March 2021. https://web.archive.org/web/20210310150248/https://configmax.vmware.com/guest?vmwareproduct=vSphere&release=vSphere%207.0&categories=2-0. dead.
  52. Web site: VMware, Inc. . Performance of VMware VMI . 13 February 2008 . 2009-01-22 . 25 December 2019 . https://web.archive.org/web/20191225162950/https://www.vmware.com/pdf/VMware_VMI_performance.pdf . dead .
  53. Web site: vSphere 6.7 Configuration Maximums . VMware Configuration Maximum Tool . VMware . 12 July 2019 . 8 March 2020 . https://web.archive.org/web/20200308084753/https://configmax.vmware.com/guest?vmwareproduct=vSphere&release=vSphere%206.7&categories=1-0 . dead .

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