Datasheet

CHAPTER 1 VMware VSphere 4 OVerView

VMw a r e eSX a n d eSXi Sc a l a b i l i t y

vSphere 4 extends the scalability of the virtualization platform in several aspects. vSphere 4 sup-

ports servers with up to 64 logical CPUs and 1 TB of RAM. Consequently, vSphere can support

up to a total of 512 virtual CPUs per single host. By increasing the number of virtual machines

that can run on single host, vSphere can achieve a higher consolidation ratio compared to earlier

versions of ESX.

At an individual virtual machine level, vSphere 4 adds support for up to eight virtual CPUs

and 255 GB of memory. With these higher per virtual machine scalability limits, you can now

virtualize more enterprise applications in your data center than before.

vSphere has also switched to 64-bit versions of VMkernel and Service Console. The 64-bit

versions offer scalability beneﬁts over 32-bit versions similar to other software applications.

These beneﬁts include the ability to address a lot more memory and better support for the newer

64-bit hardware.

VMw a r e drS

We discussed VMware DRS in detail in the “Infrastructure Services” section. Here we’ll focus

only on those DRS features that help improve scalability in vSphere deployments. DRS enables

the ongoing dynamic load balancing of server resources within a cluster. This ensures that the

applications are getting required resources all the time and no single virtual machine is bottle-

necked on resources. The optimal virtual machine placement resulting from DRS load balanc-

ing can improve application scalability in a way that you cannot beat on a continuous basis.

DRS also allows you to allocate resources to virtual machines in proportion to the priorities

established in the form of shares, reservations, and limits. For example, DRS will allocate pro-

portionally higher shares of resources to virtual machines with higher shares or will guarantee

ﬁxed quantities of memory or CPU for virtual machines based on their reservations. You can

dynamically shrink and grow virtual machine resource usage as needed without rebooting

them.

Together, the dynamic load balancing and proportional resource allocation mechanisms can

improve application scalability in vSphere deployments.

Vi r t u a l Ma c h i n e ho t -ad d Su P P o r t

Virtual hardware version 7 introduced in vSphere 4 has hot-add support for various virtual

devices:

You can hot add CPU and memory to a virtual machine when needed without rebooting it

•u

(Figure 1.15).

You can add or remove virtual storage and network devices from virtual machines without

•u

disruption.

You can hot extend virtual disks for running virtual machines without any downtime.

•u

This ability to dynamically add more resources to a virtual machine without powering it off

can help you scale virtual machines as needed. However, this functionality needs to be sup-

ported by the guest operating system running inside the virtual machine. As a result, virtual

machine hot-add support is currently supported for a limited number of operating systems only.

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