Database Reference
In-Depth Information
Figure 3.1
Three physical hosts before virtualization.
Each of these individual operating systems is responsible for providing physical
resources such as CPU, memory, disk, and network to the different applications sitting
on it.
For example, sitting on the Windows Server 2008 operating system could be a series of
applications that include a SQL Server database and a number of other applications.
The Windows operating system would provide each of those applications access to the
physical resources CPU, memory, and disk.
This would also hold true for the other servers in
Figure 3.1
.
There would be a series of
applications running on those servers, including databases and various other
applications, and each OS would provide access to its resources.
Figure 3.1
is a high-
level illustration of this before the environment is virtualized.
Hypervisor Is Like an Operating System
Think of a hypervisor in the same way as you think of an operating system. It sits on top
of the physical hardware, and just like the operating systems in
Figure 3.1
, it provides
access to resources such as CPU, memory, disk, and network. However, there are two
major differences between a hypervisor and an operating system:
A hypervisor's customer is the guest operating system running on the virtual
machines (VMs), not an application such as SQL Server or Microsoft Exchange
running on the guest operating system. Another way of saying this is that operating
systems provide services to many different programs and applications running on
them. The hypervisor provides services to the many different operating systems
running on the different virtual machines it contains.
A hypervisor shares physical resources such as CPU, memory, disk, and network
