To answer the question about purpose of nodestore:
nodestore stores the raw, unindexed parts of the data of an event. For example all event breadcrumbs and contexts are stored there. Clickhouse only stores the data you can search and aggregate by. It only has indices, so to speak.
nodestore has multiple backends. On sentry.io it is not postgres, but google bigtable. We use the postgres backend for local development and for onpremise, but for large-scale installations it is suboptimal.
We don’t have a solution right now for the storage problem in any case, sorry. One thing you should ensure actually runs is sentry cleanup, but it’s definitely possible that nodestore takes this amount of disk space.