Cloud Storage SLAs: Beware the Fine Print

If you're using a cloud-based storage service, uptime is a vital question. But getting a straight answer may be harder than it sounds.Whether your small business uses a consumer-oriented backup service like Mozy or an industrial-strength option like Amazon S3, you still need to deal with this issue. After all, cloud-based storage isn't very useful if you can't get to it.

That's especially true if you're using cloud-based storage for something more than routine backups or quick-and-dirty data redundancy. Downtime in a mission-critical application is just as devastating for a small business as it is for a global enterprise.

Enter the Service Level Agreement (SLA): Your yardstick for measuring a provider's uptime guarantees.

The first question to ask is whether a provider offers any uptime guarantees. If you're using a free online backup service, the answer may be a flat-out "no." (Don't look so shocked -- you're getting what you paid for, right?)

Using a provider whose SLA does offer uptime guarantees may sound like good news. That's probably true, but be prepared to spend some time figuring out just how good the news really is.

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Here's the problem: Different providers define terms like "uptime" and "availability" in different ways.

Let's take the Google Apps SLA as an example. According to Google, "intermittent downtime" that lasts less than 10 minutes doesn't count towards its uptime guarantees. In other words, its service may bounce up and down like a yo-yo -- but as far as Google's SLA is concerned, everything is peachy.

And then we have another problem with so many SLAs: their inscrutability.

Microsoft, for example, pledges 99.9 percent uptime in its Azure Cloud Storage Services SLA. (That's not exactly an enterprise-class uptime guarantee, but we'll set that fact aside for the moment.) The problem, as another blogger pointed out, is that it's virtually impossible to understand just what qualifies as downtime in the company's eyes.

It's pointless to hope that cloud storage providers will mend their ways and provide clear, easy to understand SLAs to their customers. After all, nobody else does. Just be aware that when a provider lays out an uptime guarantee, the exceptions are probably a lot more important to your business than the rule itself.