Why is backing up virtual machines so challenging?
There are a number of factors that make backing up virtual machines so challenging. With a physical server backup, you only have to worry about backing up the server’s contents. With a virtual machine backup, you must still back up the virtual server’s contents, but you may also need to back up the virtual machine’s configuration as well.
Another factor that can make virtual machines difficult to back up is that unlike a physical server, you can’t depend on a virtual machine to remain in the same location. Mechanisms like vMotion and live migration allow virtual machines to be moved from one host to another on an as-needed basis.
The often temporary nature of virtual machines can also make them difficult to back up. Virtual machines are rapidly deployed and can be deleted just as quickly. As such, the collection of virtual machines that you need to back up today might be different from what needs to be backed up tomorrow.
Hardware compatibility can also be an issue. Smaller organizations might want to attach a backup device directly to a host server, but virtual machines are often unable to directly communicate with local backup hardware. Finally, because multiple virtual machines can run on a single physical server, resource consumption can be an issue when performing a backup.
This was first published in April 2012