Seasons of Love and Service Level Agreements (SLA)

There is a secret relationship between a show tune and voice+data communications.

First get the dry voice+data communications part out of way:
Service-based companies that don’t sell anything you can hold in your hands… companies that sell Internet Access, or Voice Services or WANs, they all offer a Service Level Agreement (SLA) to their customers. Something to the effect of 
“We promise our service will be up and running for X% of the year."
Some companies offer X as:
99.9% or
99.99% or
99.999% or 
even 100%!

Most people know that a 100% SLA is sort of bullshit. There will be service issues. A technology glitch of some kind will get you eventually.  The real question is, how much are you going to reimburse me for my lost productivity because my internet was down and I couldn’t show my boss this amazing new cat video I found on Cheezburger. Or my entire Call Center was offline with no ability to take calls from customers who wanted to order a compilation VHS tape of The Best Cat Videos of 2015. I lost revenue, so you owe me money. 
One issue that is sort of lost in all the fluff of getting the best SLA possible: how hard is my service provider going to make it on me to get the credits I deserve? But that’s probably a topic for a different Yunderblog post.

People often forget how freakin’ hard it is to keep a large, complex network up and running reliably. So if you run an Enterprise network, how many minutes are there in a year that need to be accounted for?  How many minutes a year of down time do you need to agonizingly tell your Director of IT, or VP of IT, CIO, CEO, and Board of Directors about?

Here is the fun and lively showtune part:
"525,600 minutes. 525,600 moments so dear. 525,600 minutes. How do you measure, measure a year?"

I love that song.
60min x 24hrs x 36days = 525,600 minutes per year
Easy math.

To meet an SLA of three 9’s (as the people in my business like to call it), you can be down for 0.1% of the year. So that’s 525,600 x 0.001 = 525.6 minutes.
That’s 8.76hrs.
Think about how short of an amount of time that is for an entire year. And that’s with only three nines!
People forget how good of a level of performance that is.

To meet an SLA of four 9’s, you can be down for 0.01% of the year.
So that’s 525,600 x 0.0001 = 52.56 minutes.
That's less than an hour! For an entire year!!  WTF.
By all accounts, if your service provider is only down for an hour a year, you have a very, very, very dependable service provider.

To meet an SLA of five 9’s, you can be down for 0.001% of the year.
That’s 525,600 x 0.00001 = 5.256 minutes
Five 9’s is an EXTREMELY, VERY GOOD, RIDICULOUSLY GOOD amount of down time in a year. By any reasonable human measure it is pretty crazy to think that the promise being made is that your cat video or will be made available to anyone on the internet for all but 5.256 minutes a year. But again the real questions are:
Can your service provider truly deliver that kind of reliable service, and how hard will it be to get compensated for the down time?

That's it.
I hope you enjoyed all the math combined with one of my favorite show tunes!