Книга: Mastering VMware® Infrastructure3

VMware VMotion and Storage VMotion

VMware VMotion and Storage VMotion

If you have read anything about VMware, you have most likely read about the extremely unique and innovative feature called VMotion. VMotion is a feature of ESX Server and VirtualCenter that allows a running virtual machine to be moved from one ESX Server host to another without having to power off the virtual machine. Figure 1.5 illustrates the VMotion feature of VirtualCenter.

Figure 1.5 The VMotion feature of VirtualCenter allows a running virtual machine to be transitioned from one ESX Server host to another.

VMotion satisfies an organization's need for maintaining service-level agreements (SLAs) that guarantee server availability. Administrators can easily instantiate a VMotion to remove all virtual machines from an ESX Server host that is to undergo scheduled maintenance. Once the maintenance is complete and the server is brought back online, VMotion can once again be utilized to return the virtual machines to the original server.

Even in a normal day-to-day operation, VMotion can be used when multiple virtual machines on the same host are in contention for the same resource (which ultimately is causing poor performance across all the virtual machines). VMotion can solve the problem by allowing an administrator to migrate any of the running virtual machines that are facing contention to another ESX host with greater availability for the resource in demand. For example, when two virtual machines are in contention with each other for CPU power, an administrator can eliminate the contention by performing a VMotion of one of the virtual machines to an ESX host that has more available CPU. More details on the VMware VMotion feature and its requirements will be provided in Chapter 9.

Storage VMotion builds on the idea and principle of VMotion in that downtime can be reduced when running virtual machines can be migrated to different physical environments. Storage VMotion, however, allows running virtual machines to be moved between datastores. This feature ensures that outgrowing datastores or moving to a new SAN does not force an outage for the effected virtual machines.

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