The Synology DX517 is a 5-bay expansion enclosure designed for seamless storage scalability for compatible DiskStation models like the DS1823xs+, DS1821+, and DS1621xs+. Connecting via a dedicated eSATA port, it allows for plug-and-play setup and instant recognition through DSM. This unit supports hot-swappable 3.5" and 2.5" SATA drives, enabling online volume expansion without service downtime. Whether used to grow existing storage pools or as a dedicated local backup destination, the DX517 offers a reliable, low-maintenance solution for businesses and power users needing flexible capacity growth managed directly from the host NAS.