Genentech, Hamilton Beach, and Johnson Diversey are among a smattering of large companies that have turned off their e-mail servers and signed up for Google Gmail. And, for nearly two hours on Sept. 1, tens of thousands of employees at those companies couldn't access their Gmail accounts.

Tuesday's outage happened after Google took a small number of Gmail servers offline for maintenance, resulting in overloaded request routers that send Web queries to Gmail servers. "Gmail remains more than 99.9% available to all users, and we're committed to keeping events like today's notable for their rarity," said Ben Treynor, Google's VP of engineering, in a blog post.

That's what all Gmail users got; business users got a bit more. Google offers its large business customers one-on-one "post-mortem calls" with Google management after an outage, said a Google spokesman.

Paying customers have around-the-clock phone support, and any Gmail user can check the company's Apps Status Dashboard site on the Web, which went live last February, and is similar in style to Salesforce.com's Trustsalesforce.com status site. Google promises to put a detailed report on outages to the dashboard site within 48 hours. And, Google posted outage information to two twitter accounts Tuesday.

Johnson Diversey, a manufacturer of cleaning products that has moved 12,000 employees from Lotus Notes to Gmail, was satisfied with Google's response to the outage, said global communications director Mark Goldman. "Google kept us informed and updated throughout the process, and we believe it's making every effort to minimize disruptions to our users," he said.

Johnson Diversey's calm response can be explained by the fact that few companies expect 100 percent uptime for e-mail applications, including those run by their own IT departments. And it's unlikely that several hours of e-mail downtime stretched over a year, which is roughly Gmail's track record, will cause great harm to a business.

In fact, when they sign their Google contracts, business customers approve service-level agreements that guarantee 99.9% uptime per month, which means Gmail can be down for 43 minutes per month without penalty. If it exceeds that, free days are added to the end of a business customer's contract. Because of Tuesday's outage paying customers get three free days of Gmail.

Google could strive for an even higher guarantee, such as "four nines" or "five nines," as such measurements are known in the world of software application availability. But that would require Google to make bigger investments in hardware and infrastructure for Google Apps, which in turn could drive up subscription prices. Since e-mail is relatively benign -- an outage wouldn't stop a production line, for example -- those businesses who've signed up for Gmail are willing to tolerate the occasional blip in service as the trade-off for inexpensive email.

While uptime is important, Google's success in the business world will depend on whether it can continue to work as closely with other businesses as it's apparently working with its early adopters, so that when -- not if -- relatively brief outages occur, businesses don’t feel deserted. "It's vital that this application suite is available to our employees, and we're confident Google understands this," said Johnson Diversey's Goldman.

Pharmaceutical company GlaxoSmithKline has begun moving off of a legacy e-mail system and on to Microsoft's Business Productivity Online Suite (BPOS), a Gmail competitor, which includes monthly per-seat subscriptions to Exchange email and SharePoint collaboration software hosted in a Microsoft data center. All of the company's 115,000 employees are expected to be online by the end of 2010.

CIO Bill Louv doesn't question the big SaaS providers' technical and data center abilities. "There's no way I can run email better than Google or Microsoft," Louv said. "A 100,000-user IT shop isn't going to outperform a company that runs collaborative tools for millions and millions of people."

More importantly, Louv says, is that Microsoft has given him every indication that it takes its fledgling SaaS business seriously. "How long can Microsoft's online service be successful if they aren't known for their reliability, high performance, and integrity?" he said.

Google, meanwhile, seems to be maturing in its approach to Google Apps outages. It also had outages in February and May, and intensified communication efforts with each new one. Whether Google thrives in the enterprise will not depend so much on the occasional blip in service, but how it reacts to them.

InformationWeek has published an in-depth report on why businesses shouldn't shrug off Google's upcoming Chrome OS. Download the report here (registration required).

For Further Reading:

Gmail Outage 'A Big Deal,' Says Google

Gmail Outage Says More About Google Than Clouds

Top 10 Reasons To Outsource Your Enterprise Email To Gmail