One of the advantages of VMware vSphere is that you can move a virtual machine (VM) from one location to another, across servers, storage locations — even data centers. Physical servers don’t have that ability and that can have many implications for disaster recovery, availability, etc.
In this post, we’ll review four of the most common use cases for moving a VM from one location to another and their benefits.
- Performance: The most common use case for moving VMs is for performance. You may find that one physical server is very busy from a CPU or memory perspective, while another server is not very busy. You can move a VM from one place to another for better load balancing. This can be done with no downtime to the VMs, if desired.
- Maintenance: If you need to take a physical server down for planned maintenance, whether to do server upgrades like adding RAM or CPUs, to replace failed components, or to patch ESXi itself, you can move the VMs to other servers so that applications can stay online while you are performing maintenance. This allows you to do maintenance during normal business hours instead of overnight hours on weekends, for example.
- High Availability: If the server crashes, all of the VMs on that server will crash as well. In the physical world, access to the services provided by that server would be unavailable until the server is repaired and brought back online. With vSphere, however, when a server crashes (unplanned), the VMs can automatically restart on a different physical server. This can be extended even to include not just the loss of a server, but to an entire site with all of its servers and all (or some portion) of those VMs can be restarted on vSphere servers in a different physical site.
- Physical Server Replacement: If you need to replace a physical server with a new model, you can migrate your VMs to the new server and then decommission the old server. This can be done with no downtime to the VMs themselves.
To read more about migrating in vSphere, check out my recent white paper, Virtual Machine Migration Methods in vSphere.