Add support for arbiters
We have a situation where we are required to build in an AWS region that only has two AZs (ca-central-1). In addition, there are no other AWS regions in the country (Canada). And due to our requirement around data sovereignty, we can't host this data set within a different country.
Because of this, we can't guarantee our cluster will stay up if we lose a single AZ unless we put an arbiter in a 2nd region (since no data is copied to the arbiter). However, Atlas does not support arbiters currently. I know arbiters aren't ideal, but in this edge case, it would benefit us. With our non-Atlas MongoDB cluster we can support this model, but with Atlas, we cannot. And this may keep us from moving this particular cluster into Atlas until it is supported.
Let us know if you have any questions.
Thank you!
Kyle
shared this idea
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Patrick
commented
Looking to build a 2 region active-active system using location aware replicas and sharding. Each region would have 2 AZ deployment.
If we lose a region we will no longer have a quorum - so wont be able to fail over. We really dont want to have to pay for the data in a 3rd node where we wont have any compute resources.
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Hi Kyle, There are a number of serious downsides to using arbiters: for example it's not possible to use majority writes during maintenance if only one data-bearing node remains online temporarily.
Out of curiosity, if it were possible to deploy a third replica on GCP or Azure, would that suffice? I ask because we've had a long-term roadmap objective to enable true multi-cloud clusters on Atlas and we see situations like this, where you're looking increase in-country availability as a great use case for this.
Cheers
-Andrew
