Postgresql server causing a lot of IO activity
If you have added a lot of data and later deleted it, most likely Postgres starts auto-vacuuming process on your tables.

Auto-vacuum is designed to be rather gentle and not put heavy load on running server - otherwise it will significantly reduce system performance if it was serving live data.

Since your database is mostly empty and does not have any clients, you can fix this by performing full vacuum:

VACUUM FULL VERBOSE ANALYZE;


On a few hundred megabytes database it should not take more than a few minutes, and should stop any further activity on your database.

However, it is not recommended to perform full vacuum on production database because it locks tables as it goes - do simple VACUUM instead, or rely on auto-vacuum.