Side-by-side specifications of the Synology DS1621+ and DS1621xs+, from official datasheets. Differences are highlighted.
| DS1621+ | DS1621xs+ | |
| CPU | AMD Ryzen V1500B, 2.2 GHz | Intel Xeon D-1527 2.2/2.7 GHz |
| Cores / threads | 4 cores / 8 threads | 4 cores / 8 threads |
| RAM (base) | 4 GB DDR4 ECC SODIMM | 8 GB DDR4 ECC SODIMM |
| RAM (max) | 32 GB (16 GB x 2) | 32 GB |
| Drive bays | 6 | 6 |
| Expandable to | 16 total with 2 DX517 units | 16 total with 2× DX517 |
| M.2 slots | 2 x M.2 2280 NVMe | 2× M.2 2280 NVMe |
| Network | 4 x 1GbE RJ-45 | 2× 1GbE RJ-45, 1× 10GbE RJ-45 |
| 10GbE | optional | yes |
| Max raw capacity | 256 TB raw with 2 DX517 units | 96 TB internal; 256 TB with 2× DX517 |
| Hot-swap | yes | yes |
| Form factor | desktop | Tower |
| Released | 2020 | 2020 |
| Power consumption | 51.22 W / 25.27 W | — |
| DSM at launch | — | — |
Choose the DS1621+ if you want the cheaper, quieter, AMD-based box with 6 bays, up to 32GB ECC RAM, and optional 10GbE via add-in card. Pick the DS1621xs+ if you need the faster Intel Xeon CPU, 8GB ECC RAM out of the box with a much higher 32GB+ ceiling, built-in 10GbE, and dual M.2 slots for SSD cache. Both are 6-bay units and can expand to 16 bays with one DX517, so the real decision is CPU class plus built-in 10GbE/M.2 versus price.