The way support really works
So how can you guarantee you'll get this kind of service when your organization's electronic livelihood depends upon it?
Honestly, you can't.
Just because you paid for an expensive four-hour onsite response warranty with the SAN you just bought doesn't mean you'll get it. Or rather, that four-hour warranty probably doesn't mean what you think it means. Though terms vary from vendor to vendor, that four-hour response probably means a low-level technician will call you within four hours.
Either that or you're likely to spend at least a few hours running through a support script with someone who has very little understanding of the technology. If the cause of the problem you're experiencing isn't cut and dried (such as obviously broken hardware), you can get stuck in an interminable maze of nonsensical troubleshooting steps before anyone will dispatch a tech on site and really get to work on solving the problem.
Once that's finally done, if you aren't located in or very close to a large city, you can count on a few more hours for a tech to be dispatched, track down parts that he or she needs, and actually arrive. Then the problem still has to be identified and fixed.
Premium vs. "normal" support
Most large storage vendors have a special grade of mission-critical support for situations in which a four- to six-hour fix (at any cost) is required, but such plans tend to be very, very expensive. When you're shopping for a SAN, the cost of these warranties, often more than half of the cost of the device itself, may seem ludicrous. Maybe so -- but make sure you weigh that opinion against the cost to your company of the device being unavailable, while clueless first-tier support folks ask you inane questions.
The reasons why "normal" support is so poor vary. Many times it's a result of the vendor deciding to outsource its support. This usually opens a huge chasm between salespeople who make promises and the staff who are actually responsible for supporting what has been sold.
Unlike my mechanic, the person on the phone isn't actively trying to ensure you come back for more service or to buy a car. In most cases, the company has no skin in the game whatsoever -- it already has your money. Unless you're a huge customer, even the most sternly written complaint will usually be met with disinterest and very little action.
To be sure, much of this depends on who you are dealing with. There are certainly good and bad players out there. When you're buying, you need unbiased opinions on the vendor's reputation. Sadly, that will only get you so far. In the past two years, two major storage vendors I deal with regularly have traded places as the respectively best and worst support providers. Just because a vendor's support is well regarded now doesn't mean it will be in the future.