When choosing a cloud service provider it is important to look at the Service Level Agreement offered by the cloud service provider.  A service level agreement (frequently abbreviated as SLA) is a part of a service contract where the level of service is formally defined. First, any service that claims to have a 100% service level guarantee is lying. It is just not possible to have 100% of service all the time. The variables are multiple and many times outside of the control of the service provider and thus any mention of 100% SLA guarantee is just false.

When evaluating providers look at their published service availability. Any cloud service provider not actively publishing their availability should raise red flags.

Office 365 for example has recently launched their trust center where they actively post their up-time stats for broader public disclosure.  Previously, only current Office 365 subscribers had access those numbers. Under the new policy, the statistics will be published quarterly and will be available for everyone to view via the Office 365 Trust Center. This is important in help potential customers make the right decision.

Google Apps also has their status dashboard which is able to be viewed by the public by going to the Google Apps Status Dashboard.

Here is Microsoft’s official position on their availability with Office 365.

Since launching Office 365 two years ago, we have continued to invest deeply in our infrastructure to ensure a highly available service.  While information has been available in detail for our current customers, today we’re making this information available to all customers considering Office 365.   We measure availability as the number of minutes that the Office 365 service is available in a calendar month as a percentage of the total number of minutes in that month.  We call this measure of availability the uptime number. Within this calculation we include our business, government and education services. The worldwide uptime number for Office 365 for the last four quarters beginning July 2012 and ending June 2013 has been 99.98%, 99.97%, 99.94% and 99.97%respectively.  Going forward we will disclose uptime numbers on a quarterly basis on the Office 365 Trust Center.

Here are a few more details about the uptime number:

1. The uptime number includes Exchange, SharePoint, Lync and Office Web Apps, weighted on the number of people using each of these services. Customers use these services together, so all of these are taken into account while calculating uptime.
2. This uptime number applies to Office 365 for business, education and government. We do not include consumer services in this calculation.
3. Office 365 ProPlus is an integral part of our service offering but is not included in this calculation of uptime since it largely runs on the users’ devices.
4. Individual customers may experience higher or lower uptime percentages compared to the global uptime numbers depending on location and usage patterns.

As a commitment to running a highly available service, we have a Service Level Agreement of 99.9% that is financially backed. http://trustoffice365.com/

With any cloud service the goal is to reduce the need to babysit on-premise systems, allow for higher availability of your data, increase productivity by always having the latest versions and keep high capital expenditures to a minimum by consistent monthly payments.

Amazon also advertises and publicly posts their health status at http://status.aws.amazon.com/