Oh FFS
Cheesey...it has been possible to do exactly what you request from Central storage for the past 20 years. If your environment requires a certain level of performance from each host, and all of that performance simultaneously, that can be designed...hell, you could do it with a Data General Clariion, so long as you are willing to hang enough media behind it. The problem with those old spindle bound platforms is that business needs change, and it just takes one new LUN placed on the wrong RAID group to Bork it all up.
In these days of high(er) speed storage, stringing hundreds of disks together to get to a specific I/O level is not such a thing anymore, and a lot of arrays are built with a concept of over subscription...most environments do not run every application at 100% simultaneously, so now a storage company will look at the aggregate performance needed for the environment. If over subscription makes you uncomfortable, I would suggest you also avoid thin provisioning and most Ethernet switches.
I don't think either solution is right or wrong...but putting storage inside a server is not exactly a earth shattering new concept. For every advantage you perceive there is a drawback...centralized storage provides for a more robust data protection set and the ability to design workable large scale DR plans. It also frees the server CPU from spending cycles doing advanced calculation for things like deduplication. It makes the run book for recovery from a host failure incident much shorter and simpler.
It all depends on what you are solving for.
Personally, I never, ever make absolute statements.
Biting the hand that feeds IT
