Side-by-side specifications of the Synology RS2421RP+ and RS2821RP+, from official datasheets. Differences are highlighted.
| RS2421RP+ | RS2821RP+ | |
| CPU | AMD Ryzen V1500B | AMD Ryzen V1500B, 2.2 GHz |
| Cores / threads | 4 cores / 8 threads | 4 cores / 8 threads |
| RAM (base) | 4 GB DDR4 ECC UDIMM | 4 GB DDR4 ECC UDIMM |
| RAM (max) | 32 GB | 32 GB |
| Drive bays | 12 | 16 |
| Expandable to | 24 total with 1x RX1217/RX1217RP | 28 |
| M.2 slots | 0 internal; optional PCIe adapter | 0 internal; optional via PCIe adapter |
| Network | 4 x 1GbE RJ-45 | 4 x 1GbE RJ-45 |
| 10GbE | optional | optional |
| Max raw capacity | 108 TB per volume; 24 bays with expansion | 108 TB single volume |
| Hot-swap | yes | yes |
| Form factor | Rackmount 2U | Rackmount 3U |
| Released | 2021 | 2021 |
| Power consumption | — | 97.54 W / 49.57 W |
| DSM at launch | — | — |