Side-by-side specifications of the Synology DS1621xs+ and DS1815+, from official datasheets. Differences are highlighted.
| DS1621xs+ | DS1815+ | |
| CPU | Intel Xeon D-1527 | Intel Atom C2538 |
| Cores / threads | 4 cores | 4 cores / 4 threads |
| RAM (base) | 8 GB | 2 GB |
| RAM (max) | 32 GB | 6 GB |
| Drive bays | 6 | 8 |
| Expandable to | 16 | 10 |
| M.2 slots | 2 | 0 |
| Network | 2x1GbE, 1x10GbE | 4x Gigabit |
| 10GbE | yes | optional |
| Max raw capacity | 256 TB | 48 TB |
| Hot-swap | yes | yes |
| Form factor | desktop | desktop |
| Released | 2020 | 2015 |