Side-by-side specifications of the Synology DS1618+ and DS1621xs+, from official datasheets. Differences are highlighted.
| DS1618+ | DS1621xs+ | |
| CPU | Intel Atom C3538 | Intel Xeon D-1527 2.2/2.7 GHz |
| Cores / threads | 4 cores / 4 threads | 4 cores / 8 threads |
| RAM (base) | 4 GB DDR4 non-ECC SODIMM | 8 GB DDR4 ECC SODIMM |
| RAM (max) | 32 GB | 32 GB |
| Drive bays | 6 | 6 |
| Expandable to | 10 (with 2× DX517) | 16 total with 2× DX517 |
| M.2 slots | 2 (via optional adapter card) | 2× M.2 2280 NVMe |
| Network | 4× 1GbE RJ-45 | 2× 1GbE RJ-45, 1× 10GbE RJ-45 |
| 10GbE | optional | yes |
| Max raw capacity | 192 TB raw (with 2× DX517) | 96 TB internal; 256 TB with 2× DX517 |
| Hot-swap | yes | yes |
| Form factor | Tower | Tower |
| Released | 2018 | 2020 |
| Power consumption | 56.86 W / 25.76 W | — |
| DSM at launch | — | — |
Choose the DS1621xs+ for demanding SMB workloads: its faster 8-core AMD CPU, 8GB ECC RAM expandable to 32GB, built-in 10GbE, and two M.2 NVMe slots outperform the DS1618+’s 4-core Intel CPU, 2GB ECC expandable to 32GB, and no built-in 10GbE or M.2. Both offer six bays and expansion capability, but the DS1621xs+ supports a larger expansion pool (up to 16 bays total versus 12).