Full Eviction ~70% throughput drop over value eviction?

Let’s assume following situation.
Bucket is set up to ‘full eviction mode’ and has >1TB data with documents created using upsert operation.
Does this mean that this bucket can work correctly on 100MB RAM, if there will be no document reads, only through views (since they’re stored on disk)? In other words - if I’m using upsert, does Couchbase server store document directly on disk or it loads metadata to memory and after stores to disk?