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CHAPTER 1 VMware VSphere 4 OVerView
move virtual machines off a vSphere server for any scheduled hardware maintenance with-
out the need for any application downtime.
VMware Storage VMotion VMware Storage VMotion enables similar functionality at
the storage level. You can migrate virtual disks of running virtual machines from one
storage array to another with no disruption or downtime. Storage VMotion will help you
avoid any application downtime because of planned storage maintenance or during storage
migrations.
To reduce service disruptions because of unplanned hardware downtime, VMware vSphere
availability services include the following features:
VMware High Availability (HA) If a virtual machine goes down because of hardware
or operating system failures, VMware HA automatically restarts the virtual machine on
another ESX server within minutes of the event. VMware HA provides a much simpler and
cost-effective high-availability solution compared to traditional clustering solutions.
VMware Fault Tolerance (FT) VMware FT improves high availability beyond VMware
HA. By maintaining a shadow instance of a virtual machine and allowing immediate
failover between the two instances, VMware FT avoids even the virtual machine reboot time
required in the case of VMware HA. Thus, it prevents any data loss or downtime even if
server hardware fails. Like VMware HA, it can be a cheaper and simpler alternative to tradi-
tional clustering solutions.
VMware Data Recovery VMware Data Recovery enables a simple disk-based backup and
restore solution for all of your virtual machines. It does not require you to install any agents
inside virtual machines and is completely integrated into VMware vCenter Server. VMware
Data Recovery leverages data deduplication technology to avoid saving duplicate storage
blocks twice, thus saving both backup time and disk space.
VMw a r e VMo t i o n
VMotion enables live migration of running virtual machines from one ESX server to another
with no downtime (Figure 1.11). This allows you to perform hardware maintenance without
any disruption of business operations. The migration of the virtual machine is quite seamless
and transparent to the end user. When you initiate a VMotion, the current state of the virtual
machine, along with its active memory, is quickly transferred from one ESX server to another
over a dedicated network link, and the ESX server gets the control of virtual machine’s storage
using VMFS. The virtual machine retains the same IP address after the migration. VMotion is
the key enabling technology that allows VMware DRS to create a self-managing, highly opti-
mized, and efficient virtual environment with built-in load balancing.
vSphere supports Enhanced VMotion Compatibility (EVC) using CPU features such as Intel
FlexMigration and AMD-V Extended Migration technologies to allow migrations from older
servers to newer servers.
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