My recent post on XML appliances, referencing the observations of Thomas Rischbeck, got some pushback on the point that "The only catch is that virtual XML appliances cannot provide XML acceleration."
Thomas' actual phrase in his excellent article was: "many XML appliance vendors now chose to provide their software as a virtual appliance that can be deployed anywhere (albeit without XML acceleration)."
How much acceleration can software-based appliance provide?
Francois Lascelles pointed out in a tweet that "XML acceleration is not necessarily hardware based
and can also be provided by virtual appliances."
K. Scott Morrison provided his thoughts on the matter in his latest blog post, observing that "virtual appliances may not be as fast as hardware appliances for XML acceleration, but they do accelerate processing over conventional approaches. And one of value propositions of virtual appliances is that these provide a simple means to scale horizontally (in clouds, or in conventional virtualization farms) instead of vertically."
So, there's some additional thoughts on virtual applicances -- yes, the speed is there.
But, as Scott reminds us: "don't ever let a form factor dictate your architecture."