BACKGROUND IMAGE: iSTOCK/GETTY IMAGES
But the former three have been in the space the longest and have been very focused on delivering products that integrate very well with virtualized environments. They were the first players in the market and have developed tight integration at the hypervisor layer to make virtualized backups seamless, efficient and nondisruptive to the applications residing on VMs.
VM-specific backup apps were designed from the ground up to protect data in virtualized infrastructures, whereas legacy backup apps were designed more for traditional client/server environments. Legacy software applications typically were designed to protect multiple physical servers via an agent that gets deployed on the host.
In a physical server environment, there are often spare CPU cycles that a backup agent can use without necessarily impacting performance, although, in many cases, backup administrators still would conduct backups off-hours to avoid any potential resource contention that the backup process would place on the host.
Today's virtualized environments, on the other hand, can have dozens of applications residing on the same physical host. As a result, there is a much greater chance of resource contention, particularly if an agent has to get deployed onto each guest VM. And with more applications residing on the same server, there is a greater likelihood that some of these apps are running 24/7, so there is no backup window, in effect.
This is where VM-specific backup apps can add a lot of value. Because they integrate directly into the hypervisor kernel, they don't require individual agents on each guest VM. Moreover, they can also leverage some backup efficiency features that are native to some hypervisors, like change block tracking, which can dramatically shrink the backup window and minimize host resource contention, which is especially important in 24/7/forever environments.
VM-specific backup apps also save the cost of buying server agents and, especially, the overhead of managing an agent on each client.
Achieve virtual server backup through a mix of techniques
Tutorial: Virtual server backup tools
Essential Guide: Server virtualization and data backup