This post covers VMotion in the main – the use cases, the requirements, how it works and how easy it is to setup…
Introduction: VMotion
This topic all about the moving of the virtual machine from one location to another – occasionally this is referred to as workload protability or ‘live migration’ by industry experts or other virtualization vendors. VMware’s flagship technoloy is called VMotion. Indeed it was VMware who pioneered the technology that allows the SysAdmin to move a running VM from one physical host to another, without powering off the VM and without disconnecting users. Storage VMotion discribes similiar process by which the files that make up the VM (.VMX, .VMDK) are relocated from one datastore to another, again without powering off the VM and without disconnecting users. Finally, cold migrate describes a process by which the VM is relocated either to another host, another datastore or both – with the VM powered off. This can be neccessary because the requirements of VMotion or Storage VMotion for what ever reason cannot be met.
The requirement for VMotion and Storage VMotion to work have changed over various releases. With VMware introducing new requirements, and weakening or some case removing them altogether. For instance, early version of Storage VMotion, required that VMotion was enabled first – now Storage VMotion is built-in to the platform and does not require that VMotion be enabled first. Similiarly, early versions of VMotion required the VM to be located on Shared Storage (such as FC, iSCSI, NFS) and non-shared storage such as Local VMFS volumes were not supported. By combining the functionality of VMotion and Storage VMotion it is now possible to enjoy the benefits of workload portability without the need for shared storage – although this remains a desirable feature to many customers.
Initially, when VMotion was first demonstrated few people really appreciated how revolutionary the technology was going to be. However, once customers got over the initial thrill and disbelief, they quickly came to accept the capability as given. Now, where VMotion shows its value is in related features and technologies that leverage it. It’s these business benefits that really makes a VMotion an important feature in vSphere. For instance:
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