Side-by-side specifications of the Synology RS815RP+ and RS820RP+, from official datasheets. Differences are highlighted.
| RS815RP+ | RS820RP+ | |
| CPU | Intel Atom C2538 2.4GHz | Intel Atom C3538, 2.1 GHz |
| Cores / threads | 4 cores / 4 threads | 4 cores / 4 threads |
| RAM (base) | 2 GB DDR3 | 2 GB DDR4 non-ECC |
| RAM (max) | 6 GB | 18 GB |
| Drive bays | 4 | 4 |
| Expandable to | 4 (with RX415) | 8 total with RX418 |
| M.2 slots | 0 | 0 internal; optional via PCIe M2D18 adapter |
| Network | 4x Gigabit | 4 x Gigabit |
| 10GbE | no | optional |
| Max raw capacity | 24 TB internal; 48 TB with expansion | 56 TB raw |
| Hot-swap | yes | yes |
| Form factor | 1U rackmount | 1U rackmount |
| Released | 2015 | 2020 |
| Power consumption | — | — |
| DSM at launch | — | — |