| Brand | Synology |
| EAN | 4711174724086 |
| ASIN | B08XNG8FNL |
| MPN | RS4021XS |
| SKU | RS4021XS |
| AC input frequency | 50/60 Hz |
| Backup function | Yes |
| Certification | FCC CE BSMI VCCI RCM EAC CCC KC UL |
| Chassis type | Rack (3U) |
| Colour | Black |
| Cooling type | Active |
| Depth | 656.5 mm |
| Device class | Small & Medium Business |
| Ethernet LAN ports | 6 |
| Fan diameter | 8 cm |
| Harmonized System HS code | 84714100 |
| Height | 132.3 mm |
| Installed storage drive type | No |
| Intel Secure Key Technology version | 1.00 |
| Internal memory | 16384 MB |
| Internal memory type | DDR4 |
| Maximum CPU configuration | 1 |
| Maximum Ethernet LAN data rate supported | 10000 Mbit/s |
| Maximum RAM supported | 64 GB |
| Memory form factor | UDIMM |
| Noise Level | 44.7 dB |
| Operating relative humidity | 5 - 95 % |
| Operating temperature | 0 - 35 °C |
| PCI Express x8 Gen 3.x slots | 2 |
| Power consumption | 145.79 W |
| Power consumption HDD standby | 62.68 W |
| Power supply unit PSU capacity | 800 W |
| Processor boost frequency | 2.7 GHz |
| Processor family | Intel® Xeon® |
| Processor frequency | 2.1 GHz |
| Processor model | D-1541 |
| RAID levels | 5, 6 |
| Storage drive interface | Serial ATA II, Serial ATA III |
| Storage drive sizes supported | 2.5,3.5" |
| Storage drives supported | 16 |
| Storage temperature | -20 - 60 °C |
| Supported storage drive types | HDD & SSD |
| Type | Storage server |
| Weight | 17.4 kg |
| Width | 482 mm |