Crdb in active hot standby cluster


Would it be possible to deploy crdb in a active hot stanby scenario using 2 data centers? It can be any number of nodes but only 2 data centers. Traffic will always be consumed via one datacenter and will fall over to other if first dc is unhealthy. So strong consistency in the dc and eventual between. This is the local quorum cassandra concept which is what we are currently using.

If I understand correctly quorum will always be lost if using 2 datacenters so one wont be able to work without the other and would need atleast 3 dc with the correct locallity tags.

One way I can think of is to use the incremental backup restore functionality and do that automatically every few minutes. Some transactions will be lost but for this scenario its ok it can be handled.

To add an extra dc is not always possible because most of our clients run there own (banks).


This is not really supported by Cockroach.
Strong consistency is enforced regardless of node location.

Using zone configs, you can tell cockroach where replicas can be stored (eg: one in each datacenter), but you still cannot tell it to switch to eventual consistency, it’s just not something cockroach does.

With only two datacenters, you will always have one that has more replicas of a given range than the other. Severing the connection (datacenter going down, losing network, etc…) means that one will have the majority of the replicas for a range and will keep going, the other will have a minority and become unavailable.