What is my Azure SLA?
March 27, 2020The sudden increase in home-working as a result of the COVID-19 pandemic is putting pressure on some cloud services. The Azure Platform is experiencing capacity issues, and many of you are asking me about the Service Level Agreement (SLA) in Microsoft Cloud, with reference to high availability.
High availability definition
First we need to consider the term High availability:
High availability (HA) is the ability of a system or system component to be continuously operational for a desirably long length of time.
Availability is measured in percentage ratio, where “100%” means “never failing.” and “0%” means “never working” 😉 We can calculate this measure in following way:
Availability = (minutes in a month – minutes of downtime) * 100/minutes in a month
Using this knowledge we can say that if our service availability is 99.999%, the end user can expect the service to be unavailable for the following amounts of time:
| Time Period | Time system is unavailable |
|---|---|
| Daily | 0.9 seconds |
| Weekly | 6.0 seconds |
| Monthly | 26.3 seconds |
| Yearly | 5 minutes and 15.6 seconds |
Service Level Agreement
The second part of our definition is the Service Level Agreement:
A service-level agreement (SLA) is a commitment between a service provider and a client. Particular aspects of the service – quality, availability, responsibilities – are agreed between the service provider and the service user.
The main word for us today is: availability 😉
When we purchasing a resource from any provider, we need to consider the availability percentage and what the potential downtimes might be.
Microsoft SLA for Azure here: https://azure.microsoft.com/en-us/support/legal/sla/. We agree on the terms when we buy the services. Let’s check them out!
General rules in Azure SLA
When we go to the page we see that each Azure product is treated separately:
On the left side of the screen there are separate sections for AI+Machine Learning, Analytics, Blockchain and all other products. This means that each product can have different availability times, and different agreement details.
The screenshot below shows SLA for Azure VMware Solution by CloudSimple:
There are some differences in SLA for Azure Virtual Machines:
The availability percentage is 99% for Azure VMware Solution , and is between 99.9% and 99.99% for Azure Virtual Machines , depending on configuration.
What if the unavailability time has been exceeded?
As stated in the Service Level Agreement details, your account will be credited. For example, if the availability of your virtual machine deployed in Availability Zones was 96%, the service credit would be 25%:
You can check the service credit percentages for each Microsoft Azure product in SLA details section:
Summary
This post is a basic overview of SLA and High Availability in Microsoft Azure Platform. My intended aim was to bring you closer to this topic and give you an incentive to think about the availability of designed services. If you are an architect, administrator or IT decision maker – you should always be striving to make decisions consciously. I hope this post will help you with that! 😉
