How It Works
Three things have to take place for an end users to be a see a new IP address as a result of SiteBacker-initiated DNS changes: (1) detection time + (2) authoritative propagation + (3) recursive expiration:
- Detection time: Probe Interval (configurable by customer; 30 secs to 15 minutes) + 60 seconds (for additional processing on our side).
- Authoritative Propagation: 0 - 10 minutes. (Propagation is variable and usually under 1 minute throughout network but can be higher during periods of high activity.)
- Recursive DNS expiration (TTL value of pool records. Configurable by customer. 60 seconds to 900 seconds, usually.)
Example
Probe Interval: 2 minutes (User Configurable)
Pool Record: 2 minutes (User Configurable)
That means the time to failover is 2 minutes (probing) + 1 minute (additional processing) + authoriative propagation (0 - 10 minutes) + recursive expiration (0 - 2 minutes).
So a failover can take 15 minutes to be seen by the end user--though the most common time would be 2-6 minutes.
Please note that values like agent threshold do not affect your failover time in any significant way. If you have a probe interval of 30 seconds, all selected agents probe every 30 seconds.