Service Assurance Via the Cloud, Part 2: How Many 9’s Do You Need?

Back when 28.8 Kbps modems were de riguer and a plurality of website had strange, repeating animations that made you cross-eyed (here is a great sendup of the latter, but make sure you take some Dramamine first), no one fretted when a business website went down.

Then Amazon.com showed us the awesomeness of buying books online, broadband replaced dial-up, and pretty soon cyberspace had pretty much outpaced what William Gibson envisioned almost 30 years ago. Everything has become so interconnected that people get uneasy when a web page takes more than a few seconds to load.

So it’s been years (and years) since you could deal with infrastructure problems by redirecting users to an Under Construction animation. But given that 100 percent uptime is unattainable, how do you go about getting as close to that figure as possible?

The truth is, you don’t. “In evaluating cloud services, there are no absolutes, where the availability they offer is either good or bad,” Info-Tech lead analyst John Sloan explained to me during our recent chat. “It’s more about how their best effort compares to what your requirements are.”

To achieve an internal service level availability of “99 and five 9’s,” as John puts it, you need a great deal of infrastructure to achieve the redundancy that would allow for it.

So how do you settle on the number of 9’s you need for a given application?

You need to figure out:

  1. The importance of that app to your business;
  2. Your budget; and
  3. Your overall business objectives.

For example, a large financial services firm is going to reserve as many 9’s as possible for an application that accesses social security numbers. That app will most likely remain on the firm’s 99.999999% dedicated servers because the firm can’t afford not to protect that data.

boutique milliner, on the other hand, may lack the budget and infrastructure for more than a couple of additional 9’s. And 99 and five 9’s worth of availability is overkill for a business whose infrastructure needs consist of keeping its website online, accessing a bare-bones customer database, and managing simple transactions.

And even if the large financial services firm can provide 99 and five 9’s availability across its data center, it doesn’t follow that it should. An internal cloud may not supply the same number of 9’s as the dedicated servers, but the money saved by migrating, say, apps devoted to the firm’s recent promotions, means that the firm’s mission-critical apps can get all the 9’s they need.

Next: Nailing down the right SLAs from your potential cloud provider…


Image credit to RabiD Son



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