Attaches and manages persistent disks on Render services—mount paths, sizing, snapshots, file transfers, and single-instance constraints. Use when the user needs persistent storage, file uploads, a custom database on disk, CMS media storage, or needs to understand why their service can't scale horizontally or use zero-downtime deploys. Trigger terms: persistent disk, disk, storage, mount path, sizeGB, SSD, file uploads, snapshots, disk restore, ephemeral filesystem.