What is VMware?
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What is VMware?

Simply put, VMware develops virtualization software. VMware’s virtualization products are now a crucial part of many enterprises' IT infrastructures.

Virtualization software creates an abstraction layer over computer hardware that allows the hardware elements of a single computer—processors, memory, storage, and more—to be divided into multiple virtual computers, commonly called virtual machines (VMs). Each virtual machine runs its own operating system (OS) and behaves like an independent computer, even though it is running on a portion of the actual underlying computer hardware.

As you can imagine, virtualization enables more efficient utilization of computer hardware and enables a greater return on an organization’s hardware investment. It also enables cloud providers—public or private—to serve more users with their existing physical computer hardware.

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Virtual machines (VMs)

A virtual machine (VM) is the base unit of VMware virtualization. A VM is a software-based representation of a physical computer. An operating system (OS) running in a VM is called a guest OS.

Each VM includes a configuration file that stores the VM’s settings, a virtual disk file that is a software version of a hard drive, and a log file that keeps track of the VM’s activities, including system failures, hardware changes, migrations of virtual machines from one host to another, and the VM’s status.

VMware offers various tools for managing these files. You can configure virtual machine settings using the vSphere Client, which is a command-line interface for VM management. You can also use the vSphere Web Services software development kit to configure VMs via other programs. For example, you could enable your software development environment to create a virtual machine that it could use to test a software program.

For more information on virtual machines, see "Virtual Machines: A Complete Guide."


Using VMware products and services for virtualization brings several benefits. These include the following:

  • Improved return on investment (ROI): VMware enables you to use more of a physical computer's resources. Administrators don't like running multiple mission-critical applications on a single server OS because if one application crashes, it can make the OS unstable and crash other applications. One way to eliminate this risk is to run each application in its own OS on its own dedicated physical server, but this is inefficient because each OS might only use 30% of a server's CPU power. With VMware, you can run each application in its own OS on the same physical server and make better use of the physical server’s available CPU power.

  • More efficient use of energy and space: VMware lets you run more applications using fewer physical servers. Fewer physical servers require less space in your data center and less energy to power and cool.

  • Industry support: VMware is the foremost provider of virtualization services, with over 500,000 customers. A network of 75,000 partners supports customers with a wide variety of add-on products and services.

These are the various components of VMware virtualization and how they work.

VMware hypervisor

VMware virtualizes physical computers using its core hypervisor product. A hypervisor is a thin layer of software that interacts with the underlying resources of a physical computer (called the host) and allocates those resources to other operating systems (known as guests). The guest OS requests resources from the hypervisor.

The hypervisor separates each guest OS so each can run without interference from the others. Should one guest OS suffer an application crash, become unstable, or become infected with malware, it won't affect the performance or operation of other operating systems running on the host.

Hypervisors: A Complete Guide” gives a full overview of what hypervisors are and how they work.

VMware ESX

VMware's ESXi data center-focused hypervisor (link resides outside ibm.com) is a Type 1 or "bare metal" hypervisor, replacing the primary operating system that would interact with a computer’s physical components. It succeeds ESX, which was a larger hypervisor that used more of the host computer's resources. VMware has discontinued ESX.

VMware’s ESXi competes with several other Type 1 hypervisors:

  • VMware vs. Hyper-V: Microsoft's Hyper-V is a hypervisor product that allows you to run multiple operating systems on the same server or client computer. Like VMware's ESXi, Hyper-V is a Type 1 hypervisor that interacts with the underlying physical computing and memory resources. Hyper-V works differently to ESXi, using partitions to manage its VMs. Hyper-V must run with the Windows OS. When activated, it installs itself alongside the Windows OS in a root partition, which gives Windows privileged access to the underlying hardware. It then runs guest operating systems in child partitions that communicate with the physical hardware via the root partition. Hyper-V also ships with Windows 10 clients, competing with VMware's Type 2 Workstation hypervisors.

  • VMware vs. Citrix: Citrix offers application and desktop virtualization products and has a long track record in the virtual desktop integration market. Its main hypervisor offering is the Citrix Hypervisor (known as XenServer), which competes with VMware vSphere. Citrix’s application and desktop virtualization products compete with VMware’s Horizon virtual desktop integration product.

  • VMware vs. KVM: Both VMware ESXi and KVM are hypervisors, but KVM is part of the Linux kernel (the heart of the OS). KVM's big advantage over VMware ESXi is that it is an open source product, making its code base transparent. You can use a variety of open source virtualization management tools that integrate with the Linux kernel. As with many open source projects, they might need extra configuration work. You can also buy Red Hat Virtualization, which provides a suite of management tools for virtual servers built on KVM.
VMware and Linux

VMware relied on Linux during its early history. The early version of its hypervisor, called ESX, included a Linux kernel (the central part of an OS that manages the computer hardware). When VMware released ESXi, it replaced the Linux kernel with its own. ESXi supports a wide range of Linux guest operating systems including Ubuntu, Debian, and FreeBSD.

Desktop virtualization

VMware is a well-established server-based hypervisor, but it also sells software that virtualizes desktop operating systems. This section covers some of that software and how it works.

What is VMware Workstation?

VMware Workstation includes Type 2 hypervisors. Unlike a Type 1 hypervisor, which replaces the underlying OS altogether, a Type 2 hypervisor runs as an application on the desktop OS and lets desktop users run a second OS atop their main (host) OS.

VMware Workstation comes in two flavors:

  • Workstation Player (link resides outside ibm.com) is a free version that supports a single guest OS.

  • Workstation Pro (link resides outside ibm.com) supports multiple guest operating systems and integrates with VMware's enterprise virtualization management tools.

How to install VMware tools

There’s only one thing better than having a second OS on your desktop computer: having a second OS that can exchange data with the first. That’s where VMware Tools comes in. It is a crucial part of any VMware Workstation environment. It enables the guest OS running within the Type 2 hypervisor to work better with the host OS.

The benefits of installing VMware Tools include faster graphics performance and support for shared folders between the guest and host OS. You can use it to drag and drop files and to cut and paste between the two operating systems.

To install VMware Tools, click VM and then Install VMware Tools from the VMware Workstation menu. VMWare Workstation then mounts a virtual CD-ROM drive in the guest OS that contains the VMware Tools installer. You then access the CD-ROM image from within the guest OS and run the installer.

See the full installation instructions in the VMware Tools documentation (link resides outside ibm.com).

VMware’s Type 2 hypervisors compete with others on the market, including the following:

  • VMware vs. Virtualbox: VirtualBox is a Type 2 hypervisor produced by Oracle-owned Innotek that competes with VMware Workstation. It is a free, open source product that allows you to install and use another OS on top of the one already on your desktop or laptop. You can install VMware's products on Linux and Windows. VirtualBox supports Linux, Windows, Solaris, and FreeBSD as host operating systems. Each product has its strengths and relative weaknesses in different areas. VMware's products offer better support for 3D graphics, while VirtualBox supports more virtual disk images, which are files that contain virtual machine data.

  • VMware vs. Parallels: Parallels is a Type 2 hypervisor dedicated to running guest operating systems on the macOS platform. It competes with VMware Fusion. VMware Fusion is available for a single one-off fee, but you can only license Parallels via a subscription model.
Virtual desktop integration (VDI)

VMware offers a third model that sits somewhere between the server and desktop virtualization above—virtual desktop integration (VDI). VDI virtualizes desktop operating systems on a server.

VDI offers centralized desktop management, letting you configure and troubleshoot desktop operating systems without remote access or on-site visits. Users can access their applications and data from any device, anywhere, without the need to invest in expensive, high-powered client endpoint equipment. Sensitive data secure never leaves the server.

VMware Horizon

VMware Horizon is VMware's suite of VDI tools. It supports both Windows and Linux desktops. You can run your virtual desktops on your own premises or use Horizon Cloud to run them in multiple hosted cloud environments.

The Horizon suite includes Horizon Apps, a platform that lets you create your own custom app store for enterprise users to run on their virtual desktops. Your users can access a mixture of on-premise, SaaS, and mobile applications using a single set of login credentials.

Explore the benefits of virtual desktop integration with Dizzion Managed DaaS on IBM Cloud®.


VMware vSphere (link resides outside ibm.com) is VMware’s enterprise virtualization platform, including both the ESXi hypervisor software and the vCenter Server management platform for managing multiple hypervisors.

VSphere is available in three configurations: Standard, Enterprise Class, and Platinum. Each supports policy-driven virtual machine storage, live workload migration, and built-in cybersecurity features. The higher-end options include VM-level encryption, integrated container management, load-balancing, and centralized network management. Platinum alone supports automated responses to security threats and integration with third-party security operations tools.

Learn more about this virtualization platform by checking out VMware vSphere on IBM Cloud.


One of vSphere’s important components is vCenter Server (link resides outside ibm.com). This is the management component of vSphere. It allows you to manage virtual machine deployments across a large collection of host servers. It assigns virtual machines to hosts, allocates resources for them, monitors performance, and automates workflow. This tool can be used to manage user privileges based on a user’s own policies.

VCenter Server has three main components:

  • VSphere Web Client is the platform's user-interface, providing administrators with browser-based access to all functions

  • VCenter Server Database is the data repository for the product. It stores data necessary for server hosts to run hypervisors and virtual machines

  • VCenter Single Sign-On lets you access the entire vSphere infrastructure with a single login

The IBM Garage offers a tour of VMware vCenter Server, and you can learn more about VMware vCenter Server on IBM Cloud here.


Using a hypervisor on a host server will maximize your use of that hardware, but most enterprises users will need more VMs than they can fit on a single physical server. That’s where VMWare’s clustering technology comes in.

VMware shares resources between hosts by grouping them into a cluster and treating them as a single machine. You can then use VMware’s clustering technology to pool hardware resources between the hypervisors running on each host in the cluster. When adding a VM to a cluster, you can give it access to these pooled resources. There may be many clusters in a VMware-powered enterprise.

VMware allows you to create and manage clusters within its vSphere environment. A cluster supports many vSphere features, including workload balancing, high availability, and fault-tolerant resilience.

VMware clustering gives you access to several VMware functions to make your virtual infrastructure run smoothly and reliably:

VMware HA

VMware’s vSphere High Availability (HA) (link resides outside ibm.com) solution lets you switch virtual machines between physical hosts if the underlying hardware fails. It monitors the cluster and if it detects a hardware failure, it restarts its VMs on alternate hosts.

VSphere HA designates one host in a cluster as the “master,” the others are called “slaves.” The master communicates with vCenter Server, reporting back on the state of protected VMs and slave hosts.

VMware Fault Tolerance

While vSphere HA provides rapid recovery from outages, you can still expect downtime while it moves and restarts a VM. If you need more protection for mission-critical applications, vSphere Full Tolerance (link resides outside ibm.com) offers a higher level of availability. It promises no loss of data, transactions, or connections.

VSphere Fault Tolerance works by running a primary and secondary VM on separate hosts in the cluster and ensuring that they are identical at any point. If either of their hosts fails, the remaining host continues operating and vSphere Fault Tolerance creates a new secondary VM, reestablishing redundancy. VSphere automates the whole process.

VMware DRS

If you allow many VMs to run unmanaged across your host machines, you will get into trouble. Some VMs will be more demanding on CPU and memory resources than others. This can create unbalanced workloads, with hosts handling more than their share of work while others sit idle. VMware Distributed Resource Scheduling (DRS) (link resides outside ibm.com) solves that problem by balancing workloads between different ESXi hypervisors.

DRS, a feature of vSphere Enterprise Plus, works within a cluster of ESXi hosts that are sharing resources. It monitors host CPU and RAM usage and moves the VMs between them to avoid overworked and underused hosts. You can set these allocation policies yourself to reallocate resources aggressively or to rebalance less often.

Virtualizing the rest of the data center

VMware made a name for itself virtualizing servers and then desktop operating systems. In 2012, it announced plans to virtualize and automate everything in the data center in a concept called the software-defined data center (SDDC).

For more info on SDDCs, check out "Software-Defined Data Centers: A Complete Guide."

VMware's SDDC elements include the following:

VMware NSX

VMware NSX (link resides outside ibm.com) is a network virtualization product that allows you to define and control your IT network logically in software. You can consolidate network functions such as switching, routing, traffic load balancing, and firewalls into hypervisors running on x86 computers. You can manage these functions together from a single screen rather than manually configuring different hardware across different interfaces, and you can also apply software-based policies to automate network functions. It is the network component of VMware’s SDDC that brings the same virtualization benefits to networking, software, and computing functions.

The product supports multiple environments, including your data center, private cloud, and public hosted clouds. This makes it easier for your network to support cloud-native apps that rely on container environments and microservices.

VMware vSAN

VMware vSAN (link resides outside ibm.com) is part of VMware’s storage virtualization solution. It creates a software interface between VMs and physical storage devices. This software—part of the ESXi hypervisor—represents physical storage devices as a single pool of shared storage, accessible by machines in the same cluster.

Using VMware vSAN, your VMs can use storage on any computer in a cluster rather than relying only on a single computer, which might run out of storage. It also avoids wasting a physical computer's storage if the VMs running on that computer don't use it. VMs running on other hosts can use its storage, too.

VSAN integrates with vSphere to create a storage pool for management tasks, such as high availability, workload migration, and workload balancing. Custom policies give you full control over how vSphere uses shared storage.

VMware Cloud

VMware offers several products and services under the VMware Cloud (link resides outside ibm.com) banner. VMware Cloud Foundation, an integrated software suite supporting hybrid cloud operations, includes a range of services for software-defined computing, storage, networking, and security, and it is available as a service from a variety of cloud providers. You can deploy it in a private cloud environment via vSAN ReadyNode, a validated server configuration provided by an OEM working with VMware.

Learn more by checking out VMware Solutions on IBM Cloud.

VMware HCX (Service)

VMware HCX (link resides outside ibm.com) is a component of VMware Cloud that helps companies to use a mixture of computing environments. This gives IT teams the functionality they want at the right cost and enables them to keep more sensitive data on their own computers. The challenge is getting these VMs to work together across these different environments.

HCX is VMware's answer to this hybrid cloud complexity. It is a software as a service (SaaS) offering that lets you manage multiple vSphere instances across different environments, ranging from on-premise data centers to hosted cloud environments.

Formerly called Hybrid Cloud Extension and NSX Hybrid Connect, HCX abstracts your vSphere environment so that the VMs it manages appear to have the same IP address—no matter where they run. HCX uses an optimized wide-area network (WAN) connection to extend on-premise applications to the cloud without reconfiguration. This allows you to call on extra computing power from the cloud to maintain the performance of on-premise applications when computing demand exceeds on-premise physical resources.

You can often see this situation occur in retail. A spike in e-commerce demand might use up all your data center resources. You can keep the orders flowing and avoid frustrated customers by calling on computing resources in the cloud.

HCX lets you replicate your data to a cloud-based vSphere instance for disaster recovery. Should you need to switch to a standby server or system if your on-premise infrastructure becomes unavailable, you can do so without reconfiguring IP addresses.

Learn more about VMware HCX on IBM Cloud in our Architecture Center.

Backup and snapshots

Like physical computers, VMs need to be backed up. VMware used to provide its own, called vSphere Data Protection, but it has discontinued this product. Instead, you can use EMC's Avamar backup, recovery, and deduplication software, which powered vSphere Data Protection. There are also other third-party backup solutions available from VMware’s partners.

A VMware snapshot is a file that preserves the state of a VM and its data at a given moment in time. A snapshot lets you restore your VM to the time the snapshot was taken. Snapshots are not backups, because they only save the changes from the original virtual disk file. Only a full backup solution can fully protect your VMs.

VMware containers

Developers increasingly use containers as an alternative to VMs. Like VMs, they are virtual environments containing applications abstracted from the physical hardware. However, containers share the underlying host OS kernel instead of virtualizing an entire OS as VMs do.

For a full overview of containers, check out “Containers: A Complete Guide.”

Containers offer more agility and use physical computing power more efficiently than VMs, but they are not suitable for all cases. You might want to develop an entirely new application that divides small pieces of functionality called microservices into separate containers, making application development and maintenance more agile. On the other hand, a legacy application written to run as a single binary program might be more suitable running in a VM that mirrors the environment it is used to. You can take advantage of containers and VMs together using the VMware’s vSphere Integrated Containers (link resides outside ibm.com) feature, which bridges the gap between the two by allowing containers to run in VMware environments. It comprises three components:

  • VSphere Integrated Container Engine lets developers run containerized apps based on the popular Docker container format alongside VMs on the same vSphere infrastructure.

  • Project Harbor is an enterprise container registry that lets developers store and distribute container images so that other developers can reuse them.

  • Project Admiral is a management portal that lets development teams provision and manage containers.

AirWatch (link resides outside ibm.com) is a VMware division focusing on enterprise mobility management. Its technology is the basis for VMware’s Workspace ONE Unified Endpoint Management product, which lets you manage endpoints ranging from desktops through to small-footprint Internet of Things (IoT) devices using a single management console.

Endpoints are security vulnerabilities for companies. Attackers can gain access to the whole network by infecting a single endpoint with malware. Endpoints are also vulnerable to physical theft, making the data on them vulnerable. Managing all endpoints centrally, even when they are not on the office network, helps administrators ensure that the endpoints are properly secured and encrypted.

The endpoint management product supports a range of operating systems, from Android through to MacOS and even IoT-focused systems such as QNX. You can configure usage policies and security settings for each device on the network.

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