Yes true, but with Databases you should change the recordsize to 8 or 16k (Mysql or Postgres) and tune full_page_writes in postgres to off (zfs takes care of th

Yes true, but with Databases you should change the recordsize to 8 or 16k (Mysql or Postgres) and tune full_page_writes in postgres to off (zfs takes care of that), and just cache the metadata because the postgres-cache is better informed of what to cache.