“The appliance is dead, long live the virtual appliance.”

In a briefing with Certeon, whose recently released product, aCelera, is a virtual appliance, I was reliably informed that one of Certeon’s enterprise customers had instituted a policy that no appliances or stand-alone servers could be added to the data center without the direct permission of the CIO. It doesn’t surprise me. I’ve been hearing murmurings against appliances for months now. To me, this is more than a straw in the wind. It sounds the death knell the plug-in appliance, and to be honest it didn’t have a particularly long life.

Appliances, as we have come to know them, are ready made servers with software loaded, and maybe even configured, that you “just plug in” to the network. They appeared in the market about six or seven years ago when the form factor of servers reduced to “rack-mounted” size. Moore’s Law gave birth to them (servers shrunk to rack-mounted size) and Moore’s Law destroyed them (servers shrunk to blades). In their day, they were compelling for the following reasons:

• Took up very little space
• Minimal setup time
• Unlikely to interfere with anything else.
• Most likely enabled with remote support.
• Usually secure
• Adequately configured resources for purpose (usually)

They are no longer compelling for the following reasons:

• Take up too much space
• Need extra power and cooling
• May consume resources inefficiently
• May introduce a non-standard environment

The appliance had a remarkably short reign. You could say that it died in infancy or you could say that it evolved into a virtual appliance. Either way its time has passed.

The Virtual Appliance

A virtual appliance is an appliance without the iron. It comes with a virtual machine. Certeon’s aCelera, for example, comes with VMware ESX, although Microsoft’s Hyper-V, will be an option when it is released. (Note that there will be a commercial contest to line up virtual appliance providers between VMware and Microsoft.)

Like most appliances aCelera has a nicely focused purpose. It has the simple goal of reducing WAN latency. It does this using a 3 step compression on WAN traffic. First it applies transport layer compression (at the packet level). Next it applies protocol layer compression (both HTTP and CIFS). Finally it applies a global compression which involves keeping a record of large files that are sent across the WAN and sending only the deltas. The performance improvement this gives depends upon the nature of the traffic, but in situations where documents and other large files are regularly transmitted, it can reduce latency by 95%.

aCelera is one of those products where it is easy to know whether you have a need for it. If you have WAN traffic problems and you have some idea of the profile of the traffic then you can quite easily calculate the performance improvements it will deliver.

If you decide you have a need for it, you’ll be buying multiple units to pepper around the WAN. You can have it in two flavors. It either comes entirely soft, complete with VMware ESX (or ESXi) or it comes loaded on a Dell server. Certeon has discovered that the with-server option is often preferred in branch offices . In any event the server can be partitioned and used for other purposes during periods when its resources are not fully utilized.

And that’s the big point about virtual appliances: You can instantiate them and remove them as and when you need them and it makes very little impact on the data center.

aCelera is the first virtual appliance Ive come across, but I have no doubt that all appliance products are going to move in this direction if they haven’t already done so. The appliance as we knew it is dead.