If you thought virtual appliances - complete ready-to-run services in (typically) a VMware wrapper - were just for trying things out on, think again.

So says Dave Asprey, the VP in charge of technology strategy at Zeus Technology, which announced a virtual version of its ZXTM traffic manager last year. Asprey says that sales of ZXTM virtual machines (VMs) now exceed those of traditional hardware appliances, and are closing on the sales of ZXTM as a straight software app.

"We had assumed that virtual appliances would mostly go in to test and so on, then they'd put in a full appliance, but we have found people happy to deploy a VM in production," he adds.

"A customer can download our stuff and have it running in 20 minutes - it's so much faster than shipping a demo box. It's more scalable once sold too, as you can just download another licence."

The virtual approach is attractive partly because of its relative simplicity, he says. "IT knows how to deploy and lock-down an OS, and how to deploy apps, but it's still more work than deploying a VM. And the performance hit from virtualising isn't as bad as you might think - you can get a couple of Gigabits through a VM, and few companies actually have Gigabit pipes."

Another advantage of the virtual approach is that the virtualisation framework - the hypervisor - insulates the VM from the hardware, says Steve Harriman, marketing VP for network monitoring specialist NetQoS. That means there's no need to worry about whether a customer's server will be up to the job of running the software - as long as it's running the right hypervisor, it will run the appliance.

"Our eval units are now being shipped in VMware, and we are planning to roll it out in production where the customer has multiple units and wants to reduce the hardware count," he added.

Other suppliers offering virtual appliances include Covergence, with VMware-wrapped session border controllers for unified communications, and Kace, which has a VM version of its systems management box.