Scalable NAS with SSD cache acceleration capability Synology DiskStation DS1520+ is an ideal network-attached storage solution suitable for small office and IT enthusiasts. Two built-in M.2 SSD slots and Synology SSD Cache technology allow you to boost system I/O and application performance. The scalable storage design of DS1520+ lets you start small and expand storage capacity with Synology DX517 as your data grows. Optimize performance and capacity DS1520+ provides two built-in M.2 SSD slots so that you can take full advantage of Synology SSD Cache functionality. Add SSD cache for up to 20 times faster I/O response without using front drive bays. You can add 10 more drives with two Synology DX517 to expand storage capacity. Accelerate demanding applications