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• COLD Migration: This is the process of migrating a powered-off VM, including its configuration and DATA, from a single host to another. ONE can migrate VMs manually or set up a scheduled task to perform cold migration.  
• Hot Migration: This is the process of migrating a powered-on VM from a single host to another. It is also KNOWN as live migration because there is no need to shut down the VM.

In VMware, the CLUSTER is defined as a logical grouping of multiple ESXi hosts. It lets you ADD and remove hosts from a cluster. HA and DRS are also provided on the cluster.  

VSPHERE 6.0 introduces the concept of Virtual Volume, also known as VVol, for MANAGING virtual disks. Whenever a virtual disk is CREATED in a virtual ENVIRONMENT, VVol is AUTOMATICALLY created. At the virtual disk level, it enables array-based operations. 

Generally, iSCSI SANs consist of an iSCSI storage SYSTEM, which houses one or more storage processors. Communication between the HOST and array OCCURS over TCP/IP protocol, and ESXI hosts are configured with an iSCSI initiator. Such an initiator is either HARDWARE- or software-based. The hardware-based initiators can be dependent or independent; the software-based ones are called iSCSI software initiators. 

The following are the three port-groups configured in ESXI networking: 

• Virtual MACHINE Port GROUP: They are used for Virtual Machine Network.
• SERVICE Console Port Group: They are used for Service Console COMMUNICATIONS.
• VMKernel Port Group: They are used for vMotion, iSCSI, NFS (Network File System) Communications.

As the name suggests, port groups are groups of virtual ports on our virtual switch. In GENERAL, the port group provides a stable anchor POINT for virtual machines connected to LABELED networks by aggregating multiple ports into a single configuration. Every port group is assigned a network label, which is unique to the host. VLAN (Virtual Local Area Network) TAGS, for example, are shared by each port group member. 

DRS (Distributed Resource Scheduler), as the name suggests, PROVIDES a way to schedule and BALANCE resources ACROSS a vSphere environment. Through the use of clusters and resource pools, VIRTUAL environments are able to automatically balance available resources across hosts. DRS uses VMWARE HA (High Availability) to move VMs from one host to another to ensure that resources are evenly distributed among them. 

VMware infrastructure consists of the following components: 

• VMware ESX Server
• VirtualCenter Server
• VMware Infrastructure Client (VI Client)
• VMware Infrastructure Web Access (VI Web Access)
• VMware Virtual Machine FILE SYSTEM (VMFS)
• VMware Virtual Symmetric Multi-Processing (SMP)
• VMware VMOTION and VMware Storage VMotion
• VMware High Availability (HA)
• VMware Distributed Resource Scheduler (DRS)
• VMware Consolidated Backup (Consolidated Backup)
• VMware Infrastructure SDK

VMWARE OFFERS the following PRODUCTS: 

• VMware Mirage
• VMware PIVOTAL Container
• VMware Photon Platform
• VMware Thinapp
• VMware VCLOUD NFV
• VMware vCloud NFV Openstack
• VMware vRealize
• VMware vRealize Operations, etc.

VIRTUAL Machine DISK (VMDK) is an open file format by VMware which is used to store the content of virtual hard disks. In vSphere 5.5 and LATER versions, it can be up to 62 TB in size. Earlier, VMware PRODUCTS used the EXTENSION .dsk to store content or data or virtual disk files. 

• NFS (NETWORK FILE System): ESXi hosts use this file-sharing protocol to share files with NAS devices. Storage devices such as NAS connect to networks and enable ESXi hosts to access files. 
• VMFS (Virtual MACHINE File System): In VMware vSphere, it is a block-level file system that stores virtual machine files. In vSphere 6.0, it can also store large files up to 64TB in SIZE. 

ESXi (Elastic Sky X Integrated): ESXi (FORMERLY ESX) is a virtualization platform DEVELOPED by VMware for deploying and managing virtual machines. With ESXi, you get a very secure OS architecture that includes and integrates essential OS components like the Kernel. For efficiency, reliability, and PERFORMANCE, it's the leading choice. ESXi partitions hardware to consolidate applications and reduce costs by directly accessing and controlling underlying resources. It is a hypervisor that makes use of bare-metal virtualization technology.

Hypervisors, also known as VM monitors or VMMs, are software that creates and runs virtual MACHINES (VMs) as well as also manages and allocates resources to them. By sharing its resources in virtual ways, such as MEMORY and processing, a host computer can support multiple guest VMs. The special feature of a HYPERVISOR allows several virtual machines to run on a single physical server. As a result, it reduces: 

• Space efficiency
• Energy usage
• Server MAINTENANCE requirements.

Types of Hypervisor- 

• Type-1 Hypervisor (also known as Bare Metal or NATIVE Hypervisor)
• Type-2 Hypervisor (also known as Hosted Hypervisor)

VMkernel networking ENABLES VSPHERE to INTERACT with the outside world. It consists of FOUR core elements:   

• Virtual SAN
• Fault Tolerance
• Science storage
• VMotion

VMware's VMkernel is a high-performance operating system that runs directly on the ESXi HOST. VMkernel GENERALLY acts as an interface between VMs and the physical hardware of the system and is referred to as MICROKERNEL by VMware since it runs on bare metal, directly on VMware ESX hosts. In addition to providing hardware abstraction and operating system (OS) services, VMKernel allocates memory and schedules CPUs. In addition, it handles services such as vMotion, FAULT Tolerance, NFS, and iSCSI. In ORDER for VMs to communicate with ESXi, the VMKernel is vital. 

Virtualization generally enables your organization to run many PROCESSES at once with fewer physical infrastructures, leading to greater efficiency and cost savings. VMware manages different types of virtualizations, each having different uses in the industry. 

Types of virtualization-

• Server Virtualization: It is a type of virtualization where many virtual machines (VMs) run on one physical server. Since you do not have to buy NEW servers or expand your server room, you save floor space and money. Server virtualization is offered by a few well-known providers, such as vSphere, XenServer, Hyper-V, and RedHat.

• Network Virtualization: It refers to the process of combining all the physical network components into one virtual network. A virtual network can be composed of NICs, switches, VLANS, network storage devices, virtual network containers, and network media. This type of virtualization has the primary function of eliminating physical network device dependencies. One of its examples includes VMware NSX.

• Application Virtualization: The process involves virtualizing and hosting applications on a server so that end users can have access to them on their devices such as laptops, smartphones, and tablets. The app can be accessed via any Internet-connected device, so you don't have to log in to a desktop at your office to USE it. Its example includes VMware ThinApp, Citric XenApp, etc.

• Desktop Virtualization: Often called OS virtualization or VDI (Virtual Desktop Infrastructure), desktop virtualization is the process that enables you to run or deploy multiple virtual desktop OS on a physical server. The user may access his or her virtual desktop from anywhere since it is stored on a remote server. In this way, the need for individual CPUs is eliminated. Its example includes VMware Horizon View, Citrix Xen Desktop, etc.

• Storage Virtualization: Using storage virtualization, multiple network storage devices can be combined into a single storage device/array by POOLING their physical storage. It provides an easy way to manage storage and ensure consistent performance. Its example includes vSAN.

A virtualization process creates a virtual version of a physical device, such as a server, storage device, network device, on a physical host. On a SINGLE machine/server known as an ESXI (ESX integrated) host, several virtual machines, as well as multiple operating systems and APPLICATIONS, can be operated. It has the following advantages: 

• Increasing IT agility, flexibility, and scalability while REDUCING costs.
• Increased workload mobility, performance, and resource availability.
• Automated operations that save time.
• Simplify IT management and make it less expensive to operate.