I've been trying to make it a point to learn more about Azure offerings since I do believe it is changing the IT landscape and has some great benefits. In my opinion one of the best (and probably easiest) Azure services available is Azure SQL Databases.
One of the things found really interesting is that for "mission critical" applications you still need to use replication and, more importantly, PAY for more than one instance.
According to this link:
Use automated backups as your business continuity and recovery mechanism if your application:
- Is not considered mission critical.
- Doesn't have a binding SLA therefore the downtime of 24 hours or longer will not result in financial liability.
- Has a low rate of data change (low transactions per hour) and losing up to an hour of change is an acceptable data loss.
- Is cost sensitive.
If you need faster recovery, use Active Geo-Replication (discussed next).
And for Active Geo-replication:
Use Active Geo-Replication if your application meets any of these criteria:
- Is mission critical.
- Has a service level agreement (SLA) that does not allow for 24 hours or more of downtime.
- Downtime will result in financial liability.
- Has a high rate of data change is high and losing an hour of data is not acceptable.
- The additional cost of active geo-replication is lower than the potential financial liability and associated loss of business.
So it appears that even though the SLA for Azure SQL Databases states they guarantee 99.9 uptime, be aware if your application is mission critical you may need Active Geo-Replication to ensure availability.