In fact, I encountered a situation once where I did monitor the storage device (all central storage I have looked at has a way of externalising performance data by SNMP) for 6 months and saw the processor of the SAN 100% busy for the last month. Upon asking, the storage admins saw ‘no problems’, and suggested to look elsewhere for the performance problem.

With this in mind, operating system virtualisation is the next thing which is already creeping into the data centres……
Most companies I know, are fighting performance problems. Quite some of these performance problems are due to improper use of central storage, due to the lack of knowledge about technical implications (about which you gave an example).
The only way to combat these problems is by altering the architecture of the data center (meaning balancing the SAN throughput and the number of clients, which means reducing the number of clients in most cases), which is often rejected as a solution because this affects the cost model of central storage (making it more expensive)

Now, think about operating system virtualisation. This virtualisation means we can use a physical machine (with fixed bandwidth for IO, networking, systembus, etc.) and use it shared JUST LIKE CENTRAL STORAGE. This means that, while our IO is still cumbersome in some cases, we are going to do the exact same thing with our physical machine. Just like the central storage/SAN’s I encounter, there is no way to guarantee IO throughput for a virtual machine, nor is there for network traffic, nor is there for system bus usage. (the resources which are manageable with the mainstream virtualistion software are CPU and amount of memory)

I would be very, very happy if there is a way to manage these resources, but have come across quite some data center’s and clients, and have never encountered it.