Reply To: How stable is Office 365? Can I trust the cloud?

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@tony Redmond – from the link you posted.

Microsoft calculates the Office 365 SLA in terms of downtime, or minutes when incidents deprive users of a contracted service such as Exchange Online or SharePoint Online. As an example of the calculation, if you assume that Microsoft has 100 million active users for Office 365, the total number of minutes available to Office 365 users in a 90-day quarter is 12,960,000,000. Achieving a 99.97% SLA means that Microsoft considers incidents caused downtime of 3,888,000,000 minutes or 64,800,000 hours. These are enormous numbers, but put in the context of the size of Office 365, each Office 365 lost just 39 minutes of downtime during the quarter.

Of course, some users experienced zero downtime. Incidents might not have affected their tenant or they might not have been active when an incident happened. On the other hand, some tenants might have had a horrible quarter. Remember that Office 365 spreads across twelve datacenter regions and the service varies from region to region and from tenant to tenant, a fact that you should always remember when a Twitter storm breaks to discuss a new outage.

And that is a horrendous way to calculate it. If I have 5 days of no availability in a quarter, I don’t want to hear that the SLA for the complete Office 365 community hit its 99.9%. That is irrelevant. What is relevant is that my tenant / my users didn’t experience 99.97%. I don’t care if everybody else had 100% for the quarter, if I lost 5 days productivity at millions of Euros a day, that is a real loss for me, but due to Microsoft’s way of calculating, I’m SOL because the other tenants were AOK?