VMware vSphere 4.0 Notes

VMOTION and Storage VMOTION

VMOTION
VMware vMotion enables the live migration of running virtual machines from one physical server to another with zero down time, continuous service availability, and complete transaction integrity.

Storage vMotion
Storage vMotion enables the migration of virtual machine files from one datastore to another without service interruption.You can choose to place the virtual machine and all its disks in a single location, or select separate locations for the virtual machine configuration file and each virtual disk. The virtual machine remains on the same host during Storage vMotion.


VMware Distributed Scheduler(DRS)
Feature that allocates and balances computing capacity dynamically across collections of hardware resources for virtual machines. This feature includes distributed power management (DPM) capabilities that enable a datacenter to significantly reduce its power consumption.

VMware DRS helps you manage a cluster of physical hosts as a single compute resource. You can assign a virtual machine to a cluster and DRS finds an appropriate host on which to run the virtual machine. DRS places virtual machines in such a way as to ensure that load across the cluster is balanced, and cluster-wide resource allocation policies (for example, reservations, priorities, and limits) are enforced. When a virtual machine is powered on, DRS performs an initial placement of the virtual machine on a host. As cluster conditions change (for example, load and available resources), DRS migrates (using vMotion) virtual machines to other hosts as necessary.

VMware Fault Tolerence (FT)
When Fault Tolerance is enabled for a virtual machine, a secondary copy of the original (or primary) virtual machine is created. All actions completed on the primary virtual machine are also applied to the secondary virtual machine. If the primary virtual machine becomes unavailable, the secondary machine
becomes active, providing continuous availability.

Using VMware vLockstep technology, VMware Fault Tolerance (FT) on the ESX/ESXi host platform provides continuous availability by protecting a virtual machine (the primary virtual machine) with a shadow copy (secondary virtual machine) that runs in virtual lockstep on a separate host. Inputs and events performed on the primary virtual machine are recorded and replayed on the Secondary virtual machine ensuring that the two remain in an identical state. For example, mouse-clicks and keystrokes are recorded on the primary virtual machine and replayed on the secondary virtual machine. Because the secondary virtual machine is in virtual lockstep with the primary virtual machine, it can take over execution at any point without service interruption or loss of data.

VMware High Availability (HA)
VMware HA enables quick automated restart of virtual machines on a different physical server within a cluster if a host fails. All applications within the virtual machines have the high availability benefit. HA monitors all physical hosts in a cluster and detects host failures. An agent placed on each physical host maintains a heartbeat with the other hosts in the resource pool. Loss of a heartbeat initiates the process of restarting all affected virtual machines on other hosts. See Figure 7 for an example of VMware HA. HA admission control ensures that sufficient resources are available in the cluster at all times to restart virtual machines on different physical hosts in the event of host failure.