Google has changed its service level agreement for paid versions of Google Apps, its suite of online applications. The goal, says Google Enterprise product management director Matt Glotzbach, is to deliver service that's as reliable as telephone dial tone.

For today's mobile generation, who may lack experience with landlines, let it suffice to say that dial tone under Ma Bell was very, very reliable. Not sunrise reliable but chances were if you didn't hear a dial tone when you picked up a handset, the phone was disconnected from the wall.

Google hasn't been as consistently reliable as that. Its Postini e-mail archiving service was down for about a day in October 2009. There was a 100-minute Gmail outage in September 2009 and a more significant one in May of that year, as well as several other such incidents. Downtime happens, to Google, Microsoft, and just about every other cloud service provider you can think of.

But with millions of enterprise customers, Google aims to become more reliable. As a sign of its commitment, the company has disavowed planned downtime. "Unlike most providers, we don't plan for our users to be down, even when we're upgrading our services or maintaining our systems," wrote Glotzbach in a blog post. "For that reason, we're removing the SLA clause that allows for scheduled downtime."

Glotzbach says Google is the first major cloud service provider to make that pledge.

The company has also amended its SLA to include intermittent downtime. It used to be that outages lasting less than ten minutes were not counted as downtime. Now they count toward the total that determines whether customers receive credit under the terms of the SLA.

Gmail, the most popular app in Google Apps, was down for seven minutes in 2010. That's 99.984% uptime. Google offers credit to customers for reliability of less than 99.9%.

According to Glotzbach, Google does pretty well when compared to the competition. Citing figures from the Radicati Group, a messaging consultancy, he notes that the average on-premises e-mail system is down for 3.8 hours per month. "This suggests Gmail is 32 times more reliable than the average e-mail system, and 46 times more available than Microsoft Exchange," he wrote.

While Microsoft may be able to offer statistics that show its services in a more favorable light, what's important is that businesses can look forward to even better service in the cloud.