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You need to be careful when assigning the minimum settings or reservations because they
guarantee resources to a virtual machine. If too much CPU and memory resources are reserved,
you may not be able to start virtual machines.
New Virtual Hardware Generation
In vSphere 4.0, VMware has upgraded the virtual hardware from version 4 to version 7. This
generation of virtual hardware adds the following features:
Serial attached SCSI (SAS) virtual device for Microsoft Cluster Service This virtual
device is needed to support running Windows Server 2008 in a Microsoft Cluster Service
configuration. Later chapters in this book cover setting up a Microsoft Cluster Service con-
figuration using Windows Server 2008 and will demonstrate the use of this device.
IDE virtual device This virtual device is recommended for older operating systems that do
not support SCSI drivers.
VMXNET generation 3 VMware introduces the third generation of their paravirtualized
virtual networking adapter in vSphere 4. Refer to the “VMware vNetwork” section later in
this chapter for details.
Virtual machine hot-plug support The new virtual hardware generation enables you to
hot plug virtual devices to a virtual machine without having to power it off. You can hot add
and remove virtual CPUs, hot add and remove network cards and disks, and hot add mem-
ory to a virtual machine when using virtual hardware version 7. The support for the CPU
and memory hot-add plug-in depends upon the guest operating system support.
New virtual machines created in the vSphere environment use virtual hardware version 7 by
default. However, vSphere can run virtual machines created on hosts running ESX Server ver-
sions 2.x and 3.x.
You can find the virtual hardware version either on the virtual machine Summary tab or at
the top left of the Virtual Machine Properties window. To convert your existing virtual machines,
you first need to update VMware Tools to the latest version. You can then upgrade the virtual
hardware used by the virtual machine. Right-click the virtual machine, and the context menu
should provide you with an option to perform this upgrade (Figure 1.3).
Figure 1.3
VM hardware
upgrade
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