Lets just get straight to the point, Azure SQL Database across all service tiers gives you the customer a SLA of 99.99% up-time. This means potential unavailability periods shown below.
Good, bad, you decide. The point is that even in the cloud we “could” potentially encounter downtime. Can you improve on 99.99%? Well that was the question I asked Microsoft, I was given a “wishy-washy” answer that yes you can by using failover groups ( I’m guessing the read/write endpoint is key here ) to improve the up time. I then pressed on what sort of figure in terms of nines does this provide, to no avail.
So what happens if up time is less than 99.99% or even worse 99% (ouch). Service credits are available as shown below.
Downtime from the following DOES not count as availability issues, I picked my favorite ones with my thoughts.
- Due to factors outside our reasonable control – This ranges from natural disasters to networking device failure outside of their data centers.
- Pre – release versions of the software – that’s understandable.
- That result from the use of services, hardware, or software not provided by us – So they are talking about 3rd party services / software.
- That result from your unauthorized action or lack of action when required. Totally understand this, if I delete all my firewall rules well yes, that’s my fault.
- That result from your failure to adhere to any required configurations, use supported platforms, follow any policies for acceptable use. Here they mean unsupported operations? No idea what they mean. I tried using DBCC WRITEPAGE, it doesn’t work.
- That result from faulty input, instructions, or arguments (for example, requests to access files that do not exist) – this totally confused me.
- That result from your attempts to perform operations that exceed prescribed quotas or that resulted from our throttling of suspected abusive behaviour. Absolutely, HTTP floods are bad news.
- Due to your use of Service features that are outside of associated Support Windows. Do they mean deprecated features? No idea.
Anyway, the full list is shown here – a must read. https://azure.microsoft.com/en-us/support/legal/sla/sql-database/v1_1/
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I’ve found similar exclusions on Amazon RDS. Including this beauty:
“caused by underlying database engine software that lead to repeated database crashes or an inoperable database instance”
That said I probably trust both Azure and Amazon to achieve better up-time than the average data centre.
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That’s brilliant from Amazon. Made me smile. Totally agree with you Matthew, looking at their data centres on YouTube it’s pretty special.