The raw data behind OSM — nearly 30 GBs compressed — is Open Source and free for anyone to download and explore. Once downloaded, we use the amazing Imposm 3 (“import OSM”) to parse, tag, normalize, and store it to a Postgres database with the PostGIS spatial database extension for querying geographic objects. Imposm v3 also offers an import process that efficiently imports OSM incremental files, which we’re gearing up to do daily, or more frequently when required in the case of major natural disasters when teams of OSM contributors mobilize to support relief on the ground (an amazing effort and process that deserves its own blog post!). Currently a full OSM database import requires about 1TB of storage.

Source: How MapJam Is Building A Scalable Custom Maps Service – | StackShare