VMware ESX


VMware ESX and a different historic VMware ESX 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 ; instead, they include and integrate vital OS components, such as a kernel.
Prior to ESXi 3.0 there was only the original hypervisor named ESX, and for a while both hypervisor products existed. ESXi replaces the Service Console with a more closely integrated OS. ESX/ESXi is the primary component in the VMware Infrastructure software suite. However from version 9.0, VMware renamed ESXi to ESX despite the name having already been used before for their earlier hypervisor product.
The name ESX originated as an abbreviation of Elastic Sky X. In September 2004, the replacement for ESX was internally called VMvisor, but later changed to ESXi.

Architecture

ESX runs on bare metal unlike other VMware products. It includes its own kernel. In the historic VMware ESX, a Linux kernel was started first and then used to load a variety of specialized virtualization components, including ESX, which is otherwise known as the vmkernel component. 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, which does not include a Linux kernel at all.
The vmkernel is a microkernel with three interfaces: hardware, guest systems, and the service console.

Interface to hardware

The vmkernel handles CPU and memory directly, using scan-before-execution to handle special or privileged CPU instructions
and the SRAT to track allocated memory.
Access to other hardware 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."
The vmkernel uses the device drivers:
  1. net/e100
  2. net/e1000
  3. net/e1000e
  4. net/bnx2
  5. net/tg3
  7. net/pcnet32
  9. scsi/adp94xx
  10. scsi/aic7xxx
  11. scsi/aic79xx
  12. scsi/ips
  13. scsi/lpfcdd-v732
  14. scsi/megaraid2
  15. scsi/mptscsi_2xx
  16. scsi/qla2200-v7.07
  17. scsi/megaraid_sas
  18. scsi/qla4010
  19. scsi/qla4022
  21. scsi/aacraid_esx30
  22. scsi/lpfcdd-v7xx
  23. scsi/qla2200-v7xx
These drivers mostly equate to those described in VMware's hardware compatibility list. 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.

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.
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. 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.
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 and ESXi, but as of version 5, the original ESX has been discontinued in favor of ESXi.
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.
VMware ESX 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.
ESXi stood for "ESX integrated".
VMware ESX originated as a compact version of VMware ESX 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:
  • VMware ESX Installable
  • VMware ESX Embedded Edition
The same media can be used to install either of these variations depending on the size of the target media. One can upgrade ESXi to VMware Infrastructure 3 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,
and, following a dismissal by the court in 2016, Hellwig announced he would file an appeal.
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".
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. This followed with Hellwig withdrawing his case, and withholding further legal action.

Related or additional products

The following products operate in conjunction with ESX:
  • vCenter Server, enables monitoring and management of multiple ESX, ESXi and GSX servers. In addition, users must install it to run infrastructure services such as:
  • * vMotion
  • * svMotion aka Storage vMotion
  • * Enhanced vMotion aka
  • * Distributed Resource Scheduler
  • * High Availability
  • * Fault Tolerance
  • Converter, enables users to create VMware ESX Server- or Workstation-compatible virtual machines from either physical machines or from virtual machines made by other virtualization products. Converter replaces the VMware "P2V Assistant" and "Importer" products — P2V Assistant allowed users to convert physical machines into virtual machines, and Importer allowed the import of virtual machines from other products into VMware Workstation.
  • vSphere Client, enables monitoring and management of a single instance of ESX or ESXi server. After ESX 4.1, vSphere Client was no longer available from the ESX/ESXi server but must be downloaded from the VMware web site.

    Cisco Nexus 1000v

Network-connectivity between ESX hosts and the VMs running on it relies on virtual NICs 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 and on each ESX host a virtual Ethernet module. The VSM runs as a virtual appliance within the ESX cluster or on dedicated hardware and the VEM runs as a module on each host and replaces a standard dvS 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.

Third-party management tools

Because VMware ESX is a leader in the server-virtualization market, 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 and a plugin to monitor and manage ESX using HP OpenView, 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 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 on their hardware platforms. An example is the ESX module for Dell's OpenManage management platform.
VMware has added a Web Client since v5 but it will work on vCenter only and does not contain all features.