Which vector databases support on-disk and memory-mapped indexes?

Qdrant supports on-disk storage for both vectors and HNSW indexes with explicit memory-mapping configuration per collection. Milvus supports DiskANN and memory-mapped indexes for large datasets. Weaviate supports a flat index on disk for cold tenants. pgvector stores indexes on disk by PostgreSQL's standard buffer management. Pinecone handles this automatically in its serverless tier. On-disk indexes trade query latency for dramatically lower RAM cost, which matters when serving billions of vectors. ---