Side-by-side specifications of the Synology DS1621+ and DS1621xs+, from official datasheets. Differences are highlighted.
| DS1621+ | DS1621xs+ | |
| CPU | AMD Ryzen V1500B | Intel Xeon D-1527 |
| Cores / threads | 4 | 4 cores |
| RAM (base) | 4 GB | 8 GB |
| RAM (max) | 32 GB | 32 GB |
| Drive bays | 6 | 6 |
| Expandable to | 16 | 16 |
| M.2 slots | 2 | 2 |
| Network | 4x 1GbE RJ-45 | 2x1GbE, 1x10GbE |
| 10GbE | optional | yes |
| Max raw capacity | 256 TB | 256 TB |
| Hot-swap | yes | yes |
| Form factor | desktop | desktop |
| Released | 2020 | 2020 |
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.