The DS1520+ is the successor to the now-obsolete DS1519+ and features improved hardware specifications that result in better overall performance. According to Synology, the DS1520+ is almost 14% faster in file indexing and almost 20% faster application performance, thanks to the upgraded CPU. It’s also worth noting that the DS1519+ had only two LAN ports and only one eSATA port, and it supported only a single expansion unit.