In the Cloud world, we speak of "Availability" to indicate the time the system is up and running. Availability is usually expressed as a percentage of uptime in a given year. As a client engaging with a Cloud services provider, you will be interested to sign a service level agreement (SLA) that offers you high availability.
However, what does high availability mean exactly? If a vendor offers you 99.99% availability, this would allow the system to be only down for less than 5 minutes in a month (assuming the month has 30 days). Many vendors provide tables to indicate how their availability translates to actual downtime in a given period. Here's a detailed article on availability calculations.
There is a lot of room for interpretation, so it makes sense to take a closer look at what is covered in the guaranteed availability and how realistic that number really is.
Here are some thoughts to help with evaluation:
- If a vendor offers such a high availability, can he really deliver on this promise?
Note that every percent point the vendor offers more will cost him more as he needs to have more hardware in place. Can the vendor company be trusted in that respect? - Does this include scheduled maintenance downtime or not?
The general rule is that every scheduled maintenance or maintenance that the customer agrees to is excluded from the availability. - Make sure you are clear on what the SLA covers. Some typical hosting providers might actually not commit to any availability in their agreements.
Availability and PTC Cloud Services
At PTC Cloud Services, we include an SLA for 99.5% uptime for our applications, which goes beyond what typical hosting providers can offer. Scheduled maintenance is not counted as downtime, which is a standard treatment in the industry.
In any case, our experts in PTC Cloud Services will be happy to go through the details in our Service Level Agreements at any time to avoid misunderstandings.
If you have a question, please comment below or talk to a PTC Cloud Services expert today!