9tb should be fine for vectordb, for sure. google search is many petabytes of index with vector+semantic search, that is using ScaNN.

you could probably use the hybrid search in llamaindex; or elasticsearch. there is an off the shelf discovery engine api on gcp. vertex rag engine is end to end for building your own. gcp is too expensive though. alibaba cloud have a similar solution.

We did it in an engineering setting and had very mixed results. Big 800 page machine manuals are hard to contextualise.

There’s turbopuffer