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by mikaelronstrom 1860 days ago
In order to achieve 6 9s you need a two levels of replication, you need synchronous replication with instant failover, plus asynchronous replication to handle site failover. RonDB provides both. NDB is used in lots of telecom services where you can't make a phone call unless NDB is up. These services definitely can at times run for decades without downtime. RonDB is built on top of NDB.
1 comments
ignoramous 1860 days ago
Data durability and high availability are two different metrics.

iirc, S3 SLAs availability at 99.99; durability at 99.999999999 and 99.99999999999999 for cross-region replicated buckets.

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mikaelronstrom 1860 days ago
Correct, Availability is the amount of time you are available to read and write data. Durability is the amount of time your data is not lost. The metrics mentioned in this post are about availability. Most cloud vendors provide SLAs of 99.95% availability. One problem to solve when working with a cloud vendor is that they need to upgrade their OS images every now and then, so to get the highest availability one must integrate with the cloud APIs announcing those changes.
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