Glossary for VMware vSphere 4.0

Carole Warner Reece

I’ve been reviewing the VMware vSphere 4.0 architecture, and in the process put together the following introduction glossary. 
Note: This includes just the terms I found useful this morning…

— cwr


Extension used to identify virtual disks from outside the virtual machine. These large files can be copied, archived and backed up as easily as any other files.

Application vServices

Part of the vSphere Datacenter OS, set of services that guarantee the right levels of availability, security and scalability to all applications independent of hardware and location

Authd (Service Console)

daemon that authenticates remote console access to the virtual machine. It starts when the remote console login arrives. Authd can be configured to authenticate against an existing user database such as Active Directory.

Cloud vServices

Part of the vSphere Datacenter OS, set of services that enable the creation of internal clouds and federate the on-premise infrastructure with third party cloud infrastructure. Enables location and infrastructure independent mobility for applications running on the VDC-OS


a cluster can be viewed as an aggregation of the computing and memory resources of the underlying physical hosts put together in a single pool. Virtual machines can be assigned to that pool.


a virtual representation of the underlying physical storage resources in the datacenter.

ESX host

ESX-Managed host

ESXi 4.0 architecture

next generation hypervisor in a virtualized datacenter. With ESXi 4.0, the hypervisor is embedded directly into the server systems. The key architectural difference of ESXi 4.0 is the absence of Service Console.


a virtual representation of the computing and memory resources of a physical machine running ESX/ESXi.

Hostd (Service Console)

ESX Agent service. It runs on demand providing information to any services that need it. Hostd starts at boot time if virtual machines are configured to automatically start and automatically stop.

Infrastructure vServices

Part of the vSphere Datacenter OS, set of services that seamlessly aggregate on-premise servers, storage and network

Management vServices

Part of the vSphere Datacenter OS, set of services that that allow proactive automation and control of the virtual datacenter OS and the applications running on it

memory balloon driver

Mechanism in VMKernel to use memory allocated to idle VMs

Memory overcommit

the sum of the memory allocated to each virtual machine can exceed the total physical memory installed on the host

On-disk locking

Mechanism used by VMFS to ensure that the same virtual machine is not powered on by multiple servers at the same time.

Port Group

mechansim for setting policies that govern the connected network.

Pluggable storage architecture (PSA)

part of the Storage stack in ESX 4.0 that facilitates for a better way of doing multipathing. PSA allows storage partners to add additional intelligence for load balancing and optimal performance.

Resource Manager

component of the VMkernel is responsible for scheduling time on the host processors for each VMM process. The resource manager partitions the physical resources of the underlying server. It uses a proportional share mechanism to allocate CPU, memory, and disk resources to virtual machines that are powered on.

Resource Pool

partitions of computing and memory resources from a single host or a cluster, used to assign resources to different groups or for different purposes.

Scale out

Scaling strategy based on increasing the computing power by increasing the number of servers (aka horizontal scaling)

Scale up

Scaling strategy based on increasing the computing power of a single server by adding resources to the server (aka vertical scaling)

Service Console

management access interface into ESX host. Since the VMkernel has no means of direct user access, the service console provides command line and Web access to the ESX host for managing and monitoring the host and creating and controlling virtual machines

Storage VMotion

migrates VM home and disks to new datastore by leveraging two new technologies, namely

• Changed block tracking and

• Fast suspend and resume

Suspend Modes

Part of VMware HA, allow system administrators to suspend the automated actions taken by HA thereby preventing HA from adversely impacting system maintenance. HA has separate suspend controls for the VM Health Monitoring and Host Monitoring services

Transparent page sharing

consolidates identical memory pages into a single memory location

vCenter AppSpeed

automatically ensures application performance levels. It monitors end user response time for applications, correlates these response times with different elements in the infrastructure, and triggers remedial actions to alleviate bottlenecks

vCenter Chargeback

enables automated tracking and chargeback of costs of services to the business enabling IT to function as a utility with true visibility into operating costs

vCenter Config Control

extends policy-based change and configuration management with automated enforcement across every aspect of the virtual infrastructure

vCenter Consolidation Services

A wizard that guides the process of consolidation, including specifying consolidation settings. vCenter starts collecting statistics on the selected hosts to determine the suitability for conversion. vCenter collects metrics periodically and places the data into a table in the vCenter database.

vCenter Converter for vCenter Server

vCenter Extension that enables you to import physical machines, virtual machines and supported 3rd party images directly into virtual machines managed by vCenter

vCenter Host Profiles

simplify provisioning of new hosts by creating reusable standard server network, storage and security profiles. Also monitors compliance of VMware ESX host configurations to standard baseline profiles and automates remediation.

vCenter Lifecycle manager

enables vSphere admins to automate and manage VM provisioning processes, providing a policy-driven “system of record” for all VMs that have been requested and deployed across the datacenter.

vCenter Linked mode

Technique where an administrator can login to a single vSphere client to manage Multiple vCenter Servers or ESX hosts.

vCenter Orchestrator

enables the development of customized workflows that automate operational tasks through a simple drag and drop interface, without the need for scripting.

vCenter Server

single point of control to the datacenter. It runs on top of Windows 2003 Server to provide many essential datacenter services such as access control, performance monitoring, and configuration. It groups physical resources from multiple ESX hosts and presents a central collection of simple and flexible resources for the system administrator to provision virtual machines in the virtual environment.

vCenter Site Recovery

automates the setup, testing, and execution of disaster recovery plans on vSphere Infrastructure, ensuring disaster recovery that is rapid, reliable, manageable and affordable

vCenter Update Manager

vCenter Extension that facilitates the enforcement of security standards across ESX hosts as well as virtual machines

vCenter Update Manager

is a patch management solution that provides for patching both ESX hosts as well as virtual machines. Update manager allows you to patch virtual machines whether they are running or powered off.

vCenter Update manager

automates enforcement of standard patch policies for physical VMware ESX hosts, virtual machines and applications


Remote command line interface used in ESXi 4.0. vCLI supports both Windows and Linux and the syntax is essentially the same as the command line interface for the service console. You use vCLI for configuration functions such as host, storage, and network configuration; maintenance and patching; backing up; monitoring; virtual machine life cycle management; and log retrieval.


An Infrastructure vService that enables optimal use of every type of server resource with the lowest possible overhead allowing for the highest consolidation ratios and linear scaling.

Virtual Machine File System (VMFS)

a clustered file system, optimized for very large files like virtual machine disks and swap files

Virtual machine monitors (VMM)

responsible for virtualizing CPUs. When a virtual machine starts running, control transfers to the virtual machine monitor, which begins executing instructions from the virtual machine. The transfer of control to the VMM involves setting the system state so that the VMM runs directly on the hardware.

Virtual Switch

acts like a Layer 2 switch, used to connect virtual machines through port groups connected to uplinks connected to physical network adapters.

Virtual Thin Disk Provisioning

Virtual disk thin provisioning makes it possible to have thin Virtual machine disks to start with. The VMFS does not reserve disk space until needed and is distinct from array-based thin volumes. However, the VM see full logical disk size at all times.

VM Health Monitoring

Part of VMware HA, monitors Virtual machines for possible failures such as Windows BSOD (Blue Screen of death), frozen or hanging VMs, Stoppage of VMware tools service

VMDirect Path

mechanism by which Virtual Machines are allowed to directly access a physical device using the native driver in the Guest OS. (also known as Fixed Passthrough)


Is high-performance operating system developed by VMware that runs directly on the ESX host. VMkernel controls and manages most of the physical resources on the hardware, including memory and physical processors as well as storage and networking controllers. VMkernel includes schedulers for CPU, memory, and disk access, and has full-fledged storage and network stacks.

VMkernel hardware interface

includes device drivers for storage and network devices. These drivers provide hardware-specific service delivery, hiding hardware differences from ESX host and virtual machine users.

VMkernel resource manager

partitions the physical resources of the underlying server. It uses a proportional share mechanism to allocate CPU, memory, and disk resources to virtual machines that are powered on.

VMkernel swap file

Last resource used if multiple virtual machines need their full allocation of memory, ESX Server will swap their memory regions to disk (on a fair-share basis governed by the memory resource settings you have assigned to each virtual machine); causes performance to be noticeably slower


enables the migration of live virtual machines from one physical server to another without service interruption, resources can be dynamically reallocated to virtual machines across physical servers

VMware Converter Server

is a migration tool that automates the process of creating VMware virtual machines from physical machines, other virtual machine formats and third party image formats. (Migrates other physical servers to VMs)

VMware Distributed Power Management (DPM)

helps manage power by consolidating servers when demand is low, powering off inactive hosts, working in concert with DRS

VMware Distributed Resource Scheduler (DRS)

Using VMotion and an intelligent resource scheduler, VMware DRS automates the task of assigning virtual machines to servers within the cluster to use the computing and memory resources of that server.

VMware Fault Tolerance (FT)

allows users to create a zero-downtime configuration for their virtual machines at a fraction of the cost of traditional fault tolerant solutions. FT utilizes VMware’s ‘Record Replay’ technology by recording all non-deterministic I/O operations of a VM and replaying it on a secondary host. It creates virtual machine “pairs” that are fully redundant instances.

VMware High Availability (HA)

offers a simple and low-cost high-availability alternative to application clustering. This is a Clustering Service aimed to provide immediate recovery, with minimal downtime for applications in case of host or virtual machine failure

VMware Lab Manager

provides application developers and testers with on-demand access to a library of multi-tier application configurations, reducing provisioning delays and freeing IT for more strategic tasks

VMware Stage Manager

automates the release management process, enabling application administrators to swiftly and accurately introduce new or updated applications into production

VMware Tools

a suite of utilities that enhances the performance of the virtual machine’s guest operating system and improves management of the virtual machine. The installers for VMware Tools for Windows, Linux, FreeBSD, and NetWare guest operating systems are built into ESX host as ISO image files.

VMware Virtual SMP

add-on module to VMware ESX host that makes it possible for a single virtual machine to span multiple physical processors. Virtual SMP allows a single virtual machine to use up to eight physical processors simultaneously.


a collection of two networking technologies – VMDirect Path and vNetwork Distributed Switch

vNetwork distributed services

enables the network to be treated as an aggregated resource with a global vSwitch at the datacenter level, moving the management function away from single ESX host virtual switch management to the datacenter level. Network information associated with virtual machines becomes mobile.

vNetwork Distributed Switch

framework that separates the Control Plane from the standard vSwitch in ESX and moves it to the vCenter at the Data center level. (Data plane stays with vSwitch at the ESX host)

vNetwork Distributed Switch (vDS)

abstracts the configuration of virtual networking from the host level to datacenter level, simplifying the setup and allowing the delivery of cluster wide networking services. The vNetwork Distributed Switch enables the preservation of all network and security policies when a virtual machine is being migrated


Virtual network interface card, the operating system and applications talk to the vNIC through a standard device driver or a VMware optimized device driver just as though the vNIC is a physical NIC. The vNIC has its own MAC address and one or more IP addresses and responds to the standard Ethernet protocol exactly as a physical NIC would.

Vpxa (Service Console)

vCenter Agent service. Vpxa runs when the server is added to vCenter.


vServices abstract, aggregate and allocate the hardware resources to achieve highest shared resource efficiency

vShield Zones

an add-on component which sits as a thin layer between Virtual machines and the Virtual Switches that acts as a virtual firewall providing

  • Logical partitioning of VMs into network zones
  • Visibility into and monitoring of network data flows
  • Control of network data flows using application and service aware rules based on the virtual infrastructure logical containers


A next generation data center operating system that virtualizes the entire IT infrastructure including servers, storage, and networks. It groups these heterogeneous resources and transforms the rigid, inflexible infrastructure into a simple and unified manageable set of elements in the virtualized environment.

vSphere Client

User access interface that allows users to connect remotely to the vCenter Server or individual ESX Servers from any Windows PC. It is the primary interface for creating, managing, and monitoring ESX host, Virtual machines, and their resources

vSphere Web Access

Web interface that allows virtual machine management and access to remote consoles; can perform basic virtual machine management and configuration and get console access to virtual machines.


allows for optimized storage access through a Para-virtualized scsi disk driver leading to greater than 200,000 I/O operations per second and lower than 0.2 ms latency, comfortably exceeding the requirements of most large and intense workloads


A virtual switch, or vSwitch, works like a layer-2 physical switch. Each server has its own virtual switches.

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