Who invented ESXi?

ESXi, short for Elastic Sky X Integrated, is a bare-metal hypervisor developed by VMware for running virtual machines and containers. As a type-1 hypervisor, ESXi is installed directly onto server hardware, allowing for greater efficiency and performance compared to hosted architectures.Who invented ESXi?But who originally invented this widely used enterprise virtualization platform? Read on to learn about the origins of ESXi and the VMware engineers who helped develop it into an industry-leading product.

The History Behind ESXi

The initial precursor to ESXi first emerged in 1999 when VMware released VMware Workstation, allowing operating systems to run in virtual machines on desktop computers. Following Workstation, VMware later developed two seminal enterprise-focused products:

  • VMware GSX Server (2001) – Hosted virtualization architecture installed on top of an existing OS.
  • VMware ESX (2001) – Bare-metal “virtualization layer” hypervisor installed directly on server hardware.

ESX was VMware’s first bare-metal hypervisor product for the data center and was created by Scott Devine, Edouard Bugnion, and Mendel Rosenblum – the founding engineers of VMware. Together with CEO Diane Greene, they recognized the potential benefits of running virtual machines natively on x86 servers without a separate underlying OS.

Over the next several years, the core ESX engineering team continued enhancing the hypervisor’s management capabilities, performance, reliability, and ecosystem integration. Major releases included Virtual SMP, Virtual Center management, VMFS clustered filesystems, VMotion live migration, DRS clustering, High Availability, and centralized backup.

In 2006, seeking an even more lightweight and stable platform optimized for embedding on OEM servers, VMware made a strategic decision to re-architect ESX 4.0 into a new bare-metal hypervisor labeled VMware ESXi.

The Birth of ESXi

ESXi was engineered from the ground up for embedded installations on enterprise-grade hardware. To reduce the attack surface and TCO, ESXi omitted any Linux OS dependencies allowing it to boot quickly with a compact ~32MB memory footprint. The smaller codebase improved security and reliability critical for server-class deployments. Live patching was also added to allow hypervisor updates without downtime.

Leading the ESXi development was longtime VMware Fellow and SVP of R&D Steve Herrod. Reporting to Herrod, the core ESXi engineering team included:

  • Arun Shroff – Lead Architect
  • Santosh Balasubramanian – Filesystems & Storage
  • John Arrasjid – Core Platform & Performance
  • Cormac Hogan – Storage & Availability
  • Bill Lee – Installer & Packaging
  • Tom Tkacik – Embedded Deployment & OEM Partnerships
  • Zach Smith – User Experience & Management UI
  • Duncan Hardie – Security Architect

Together they introduced innovative capabilities into the new ESXi platform:

  • Hardware abstraction – Broad hardware compatibility via BIOS-level drivers.
  • Stateless architecture – Diskless boot, persistent-cache design for embedded use.
  • VIBs – ESXi was designed for modular VIB installation of drivers and plugins.
  • pNFS – Native parallel NFS client boosting NAS performance.
  • SSL Certificate Management – Simplifying PKI identity & encryption.

The initial release of VMware ESXi 3.5 in December 2007 brought enterprise virtualization to a new level.

Growth & Maturity of ESXi

The subsequent decade saw massive industry adoption of ESXi for virtualizing business-critical production workloads at scale. New versions added features for clustering, networking, availability, storage, security, automation and hybrid cloud integration.

VMware also configured ESXi as the heart of their bundled vSphere platform – combining the hypervisor together with management tools like vCenter Server and vSphere Client.

Today, hundreds of enterprises across every industry segment rely on ESXi and vSphere to efficiently utilize IT infrastructure, reduce costs and enable digital transformation. Axis Communications, BASF, Swiss Re, Telefonica, and Wendy’s are among the many notable global brands using ESXi in their data centers and hybrid clouds.

The hypervisor runs over 150 million workloads worldwide thanks to its robust ecosystem of server, hardware and software partners like Cisco, Dell, HPE, IBM, Lenovo, NetApp and Pure Storage. Independent software vendors develop customized solutions on ESXi to meet every organizational need.


In summary, VMware ESXi originated from the initial ESX bare-metal hypervisor engineered by Rosenblum, Bugnion and Devine in 2001. As ESX matured over 5 years into an industry-leading virtualization platform, Herrod and an innovative development team created ESXi – architected from scratch specifically for embedded use on x86 servers.

Debuting in 2007, ESXi delivered stateless operation, compact modular design and enterprise-class virtualization capabilities that still underpin 21st century data centers. What began as a research project at Stanford is now a foundational IT infrastructure platform enabling leading global companies to optimize resource utilization as they digitally transform.

Key Takeaways

  • ESXi was engineered by VMware as a lightweight, embedded-ready successor to ESX – their original bare-metal hypervisor.
  • Scott Devine, Edouard Bugnion and Mendel Rosenblum invented the initial ESX product later built upon by the ESXi team.
  • Lead architect Steve Herrod assembled an all-star group of technologists to redesign ESX into ESXi for OEMs.
  • Released in 2007, ESXi introduced hardware compatibility, modular architecture and enterprise grade features.
  • Today, ESXi and vSphere power 150 million+ VMs for businesses across every industry.

Frequently Asked Questions

  1. Who originally created ESXi?
    ESXi was developed by an engineering team at VMware led by Steve Herrod. They set out to reinvent VMware’s ESX hypervisor for embedded installations. 
  2. When was the first ESXi version released?
    The initial generally available ESXi 3.5 release debuted in December 2007 after being announced earlier that year at VMworld. 
  3. What advantages did ESXi have over ESX?
    ESXi was lighter, faster booting, stateless, modular, more secure, and tailored for embedding directly onto x86 servers – ideal for OEM partnerships. 
  4. What were some key innovations in ESXi?
    Hardware abstraction for broad compatibility, smaller concentrated code base, VIB plug-ins, SSL management, persistent caches, pNFS performance, diskless operation. 
  5. Who founded VMware and developed the first hypervisors?
    VMware founders Edouard Bugnion, Scott Devine and Mendel Rosenblum engineered the initial GSX Server and ESX products later built upon by the ESXi team. 
  6. Is VMware ESXi open source?
    No, ESXi is a proprietary commercial product supported by VMware although it does integrate with open source technologies like Linux, OpenStack, Kubernetes and OVS. 
  7. Who uses VMware ESXi today?
    Over 750k customers including most major enterprises like BASF, Swiss Re, Axis Communications and Wendy’s. It also embedded by server OEMs like Cisco, Dell, HPE, Lenovo. 
  8. What is included in the VMware vSphere bundle?
    vSphere packages combine the ESXi hypervisor together with management tools like vCenter Server and vSphere Client.
  9. Does ESXi run on any server hardware?
    Yes, ESXi leverages hardware abstraction to support most modern x86 servers from vendors like Cisco, Dell, HPE, IBM, Lenovo, Super Micro 
  10. Can you vMotion live migrate VMs on ESXi?
    Yes, vMotion is a key capability for zero-downtime migrations across ESXi hosts in a vSphere cluster. 
  11. What OS runs underneath ESXi?
    As a Type-1 hypervisor, ESXi is installed directly on bare-metal server hardware without needing a separate underlying OS. 
  12. What are the most recent major releases of ESXi?
    The latest generally available releases are ESXi 7.0 U3 released in 2021 and ESXi 8.0 initially launched in 2022. 
  13. Does ESXi support containers like Kubernetes?
    Yes, through runtimes like VMware vSphere Integrated Containers users can deploy Docker containers managed by Kubernetes on ESXi alongside VMs. 
  14. What does the ESXi embedded host client allow?
    The ESXi embedded host client is a browser-based UI for administering single ESXi hypervisors without needing vCenter connectivity. 
  15. Is VMware hardware compatible list important?
    Yes, the VMware HCL provides validated server, storage, network and software compatibility with ESXi to avoid potential issues. 
  16. Who leads current ESXi engineering at VMware?
    The latest ESXi releases were overseen by Krish Prasad as senior vice president and general manager of VMware Cloud Platform Business Unit. 
  17. How is ESXi licensed?
    VMware offers various ESXi and vSphere licensing editions from free basic to production enterprise plus with customizable options. 
  18. Does ESXi integrate with public clouds?
    Yes, through hybrid capabilities like VMware Cloud on AWS, Azure VMware Solution, Oracle Cloud VMware solution etc that run native ESXi in the cloud. 
  19. Can third party tools manage ESXi?
    Yes. In addition to vCenter Server, there are independent management platforms from vendors like Nutanix, RedHat, Citrix, IBM, and SUSE that work with ESXi. 
  20. Is ESXi only for vSphere environments?
    No. Many organizations deploy standalone ESXi hypervisors outside vSphere for edge computing, retail stores, manufacturing plants etc. ISVs also directly integrate custom software with ESXi.

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