Datasheet

infraStructure SerViceS
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In the next sections, we will discuss each of these vCompute services in detail.
VMw a r e eSX a n d eSXi
VMware ESX and ESXi are the most widely deployed virtualization hypervisors, and they form
the robust foundation of VMware vSphere. VMware ESX and ESXi use bare-metal architecture;
in other words, they install directly on the server hardware, without the need for a host operat-
ing system.
Virtualization Architectures
Virtualization products for x86 servers commonly use two types of architectures: a hosted archi-
tecture or a hypervisor architecture. The hosted, or type 2, virtualization products run on top of
the Windows or Linux host operating system. The host operating system controls the access to the
physical resources, and virtual machines run as applications alongside other software on the host
machine. The VMware Workstation, Fusion, and Server products are examples of hosted virtual-
ization architecture.
Bare-metal hypervisor, or type 1, virtualization products run directly on top of the hardware with
direct access and control of the hardware’s resources. Since they have direct access to the hardware
resources rather than going through a host operating system, the hypervisor products are more
efficient than hosted virtualization products, and deliver greater scalability, robustness, and per-
formance. VMware ESX and ESXi are examples of bare-metal hypervisor architecture.
Virtualization Technologies
VMware ESX and ESXi offer a choice of three virtualization technologies (Figure 1.2):
Binary translation
•u
Hardware-assisted virtualization•u
Paravirtualization•u
Binary translation is the virtualization technique that VMware invented for x86 servers. The x86
processors were not designed with virtualization in mind. These processors have 17 CPU instruc-
tions that require special privileges and can result in operating system instability when virtualized.
The binary translation technique translates these privileged instructions into equivalent safe
instructions, thus enabling virtualization for x86 servers. Binary translation does not require any
specific features in the x86 processors and hence enables you to virtualize any x86 server in the
data center without modifying guest operating system and applications running on it.
Hardware-assisted virtualization relies on the CPU instruction set and memory management
virtualization features that both AMD and Intel have recently introduced in the x86 processors.
The first generation of these hardware-assisted virtualization processors, called AMD-SVM and
Intel-VT, only supported CPU instruction set virtualization in the processors. This alone did not
perform fast enough for all different workloads, compared to the binary translation technology.
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