VMware Inc. is a software company that develops many
suites of software products specially for providing various virtualization solutions. There are many
cloud products,
datacenter products,
desktop products and so on. VMware has moved from being just a Virtualization company, though it started as one.
VMware Vsphere or simply known as vSphere is a software suite that
comes under data center product. vSphere is like Microsoft Office suite
which has many softwares like MS Office, MS Excel, MS Access and so on.
Like Microsoft Office, vSphere is also a software suite that has many
software components like vCenter, ESXi, vSphere client and so on. So,
the combination of all these software components is vSphere. vSphere is
not a particular software that you can install and use, “it is just a
package name which has other sub components”.
ESXi, vSphere client and vCenter are components of vSphere. ESXi
server is the most important part of vSphere. ESXi is the virtualization
server. It is type 1 hypervisor. All the virtual machines or Guest OS
are installed on the ESXi server. To install, manage and access those
virtual servers which sit on top of ESXi server, you will need other
part of vSphere suit called vSphere client or vCenter. Now, vSphere
client allows administrators to connect to ESXi servers and access or
manage virtual machines. vSphere client is installed on the client
machine (e.g. Administrator’s laptop). It can also be installed on the
same physical server where ESXi is installed. The vSphere client is used
from client machine to connect to ESXi server and do management tasks.
So now what is vCenter? Why we need it? Try
cloning existing virtual machine using just a vSphere client without vCenter server and you will see it is impossible.
vCenter server is similar to vSphere client but it’s a software with
more power. vCenter server is installed on Windows Server or Linux
Server or desktop/laptop. VMware vCenter server is a centralized
management application that lets you manage virtual machines and ESXi
hosts centrally. vSphere client is used to access vCenter Server and
ultimately manage ESXi servers. vCenter server is compulsory for
enterprises to have enterprise features like vMotion, VMware High
Availability, VMware Update Manager and VMware Distributed Resource
Scheduler (DRS). For example, you can easily
clone existing virtual machine in vCenter server. So vCenter is another important part of vSphere package. You have to buy vCenter license separately.
vSphere is a product suite,
ESXi is a hypervisor installed on a physical machine.
vSphere Client is installed on laptop or desktop PC and is used to access ESXi Server to install and manage virtual machines on ESXi server.
vCenter server is installed as virtual machine on top of ESXi
server. vCenter server can also be installed on different standalone
physical server, but why not virtualize it too right? vCenter server is a
vSphere component which is mostly used in large environment where there
are many ESXi servers and dozens of virtual machines. The vCenter
server is also accessed by vSphere client for management purpose. So,
vSphere client is used to access ESXi server directly in small
environment. In larger environment, vSphere client is used again to
access vCenter server which ultimately manages ESXi server.
Virtualizing the vCenter server.
If the ESXi host that houses the virtual vCenter server becomes
inaccessible, then the services are interrupted and you cannot connect
to the server. This will cause all sorts of headaches. The only solution
is to log into each ESX host and see where the vcenter server is
present. You can build a physical vCenter server and domain controller
to alleviate this issue. Although you can virtualize any application, I
do not think all applications should be. Just some admin advice and
experience when planning your virtual environment. However, this can be
addresses by getting one or two extra hosts so vcenter can restart
itself on another host.
