In addition to providing rack space and managing servers and storage, many hosting service providers also look to manage the applications that run on their customers' Web sites. Reliability is critical in the Web hosting arena, and competitive pressures are even driving a few hosting providers to make unrealistic promises. In February, for example, Electronic Data Systems offered a service level agreement that promised 100 percent availability for Web sites and applications that EDS is hosting. This is raising the bar pretty high.

Other service providers have often promised 99.99 percent (commonly referred to as "four nines") uptime, which gives them a cushion of about 53 minutes of outage time a year when they can down the servers briefly for regularly scheduled maintenance. A few have even touted "five nines," or 99.999 percent availability, which narrows the margin for error considerably.

While these claims are suspect in their own right, promising 100 percent uptime seems to be over-reaching a little bit further. Even if you offer "nines to the nth degree" availability, you're still not going so far as guaranteeing 100 percent availability. One hundred percent availability doesn't leave much room for mistakes and disasters, especially these days when there's so much for Webmasters to worry about, from cyberterrorism threats to over-subscribed Webcasts that overload the server.

We all know that Internet connections go down, that Web sites become temporarily unavailable or fall prey to denial of service attacks. It's not uncommon for an errant Java script to crash a Web application. Indeed, EDS seems to be hedging the uninterrupted claim, backing the offer with a "time-to-repair commitment as short as 15 minutes for fully redundant systems" and providing service credits that accumulate from the first minute of downtime. That's certainly comforting if you're worried that the actual uptime might fall a little short of the 100 percent mark.

The "fully redundant" part also sounds a little fishy. Does that mean you have an extra hard drive mirroring your hard drive, and maybe a third drive just for grins? How about an extra server mirroring your server, and uninterruptible power supplies backing up the electricity for the servers, disk arrays, and air conditioner, and while you're at it, an extra system administrator so one of them can go to lunch.

The Web hosting market has grown more competitive with today's economic slowdown. With fewer companies launching Web sites and scaling back plans for multimedia Webcasts and similar brand-building and bandwidth-hogging activities, hosting providers have needed to focus on niche industries and promote unique capabilities to differentiate themselves.

The claim of perfect uptime is one such strategy. So 100 percent uptime doesn't necessarily mean availability around the clock 24/7/365. You can just see EDS founder Ross Perot snickering about that bit of slick salesmanship.

Old Ross moved on from EDS years ago to hang out with Larry King, but his spirit still lives on. And you can just hear the "giant sucking sound," as Perot put it, while this claim deflates on its own dubious merits.