A survival goal dictates how many simultaneous failure(s) a multi-region database can survive. All tables within the same database operate with the same survival goal. Each database is allowed to have its own survival goal setting.
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Allowed survival goals include:
ZONE(default): Databases configured to survive zone failures have 3 voting replicas for every range, all in the home region. To support low-latency reads from other regions, one non-voting replica is placed in each non-home region.
REGION: Databases configured to survive region failures have 2 voting replicas in the home region, and 3 voting replicas in non-home regions. This enables fast reads from within the home region and ensures minimal disruption in case one node fails, since the home region has two possible leaseholder candidates.
ZONE survival goal if:
- You can accept a single node failure up to an entire zone failure. If multiple zones fail in the same region, the database may become unavailable.
REGION survival goal if:
- The database must remain available, even if a region goes down.
- You can accept the performance cost: write latency will be increased by at least as much as the round-trip time to the nearest region. Read performance will be unaffected.
- The database can be or already is configured with 3 or more database regions. At least three database regions are required to survive region failures.