Thanos doesn't have production support for local storage either. The only stable storage providers for it are google, amazon, and azure's object stores.

https://thanos.io/storage.md/

Interestingly, it looks like Cortex's support for local storage and object stores comes from using Thanos's storage engine. So once it's production ready in Thanos it will probably be production-ready in Cortex shortly thereafter.

https://cortexmetrics.io/docs/operations/blocks-storage/

I think for Cortex your safest storage options now are Bigtable, DynamoDB, or Cassandra.

I may have misinterpreted what they meant by local storage! I was reading that as having a local copy of the TSDB available to Prometheus, (eg: how Thanos works) versus Cortex which doesn't store metrics locally (IIRC).

What you said is correct and makes sense. Though, I would suspect either choice works with any S3 compatible API that can run on local storage, but I know that isn't necessarily what's meant by "local storage".

"local storage" = I don't want to install yet another gizmo just to store data, nor do I want to use an external service for that

Batteries included.