SLA: Service Level Agreement (referred to as: SLA, full name: service level agreement). Is a mutually accepted agreement under certain expenses to protect the performance and availability of services between the service provider and the user-defined. Usually this is the main factor driving the cost to provide quality services.
Defined SLA sources of Baidu, which in the end is what does that mean?
We often see Internet companies usually shouting slogans, this year we must do three 9,4 nines, namely 99.9%, 99.99%, and even 5 9, that is 99.999%.
9 represents so much of what does it mean?
First, the concept of the SLA, the Internet company, is the site of a guarantee service availability. 9 more year-round service on behalf of the longer time available services more reliable, shorter downtime, and vice versa.
9 to calculate how much is it?
The year it took 365 days to do the calculation to see how long it down a few times to 9 can do to achieve!
1 year = 365 days = 8760 hours
99.9 = 0.1% = 8760 * 8760 * 0.001 = 8.76 hours
8760 * 99.99 = 0.0001 = 0.876 hours * 60 = 0.876 = 52.6 minutes
8760 = 99.999 * 0.0876 = 0.0876 hours = 0.00001 * 60 = 5.26 minutes
From above, the year down 5.26 minutes in order to achieve 99.999%, ie 5 9. And so on, to reach 6 9 9 and more, it can be said to be very difficult now.
How to do more 9
Each company is different definitions of several 9, the Internet companies are now at least 99.99. Like a number of government websites, such as social security fund and other, often trouble-free service is not available, 99.9 can do pretty good.
If the service we provide availability of the lower, the greater the losses caused by the mean, to say the least, if it is particularly important moment, perhaps in a minute, you might lose because service is not available and a big the orders, which are unexpected. So, as long as possible in order to enhance the availability SLA maximize business productivity.
9 To do more, we must constantly monitor their service, the service hung timely recovery services. Like taking a trip by car, first of all check the tires, but will have to prepare a spare tire same reason.