Securing your business assets
The 16-bay RS4021xs+ provides solid data security and lightening-fast performance with over 234K 4K random read IOPS and 6,258 MB/s sequential read throughput1. Together with its 8-core processor, ECC memory, advanced snapshot technology, and built-in 10GbE connectivity, the RS4021xs+ can support large multi-user environments while handling data-intensive workloads.
Intel® Xeon® D-1541 8-core 2.1 GHz
Built-in dual-port 10GbE
16 GB ECC DDR4 Up to 64 GB
Up to 40 drive bays with RX1217(RP)
Engineered for service continuity
The RS4021xs+ ensures mission-critical data is always available, enabling businesses to deliver the best results, even in the face of disaster.
Dual PSUs provide protection against a PSU failure or accidental cord removal while hot-swappable fans can be replaced without powering down the system.
Maximize service availability
Synology High Availability (SHA) pairs two identical units together creating an active-passive cluster with minute-level failover.
Next-generation file system
Btrfs prevents data corruption and reduces maintenance overheads with advanced storage technologies and optimized snapshots.
Intel Xeon D-1541
8-core 2.1 (base) / 2.7 (turbo) GHz
Hardware Encryption Engine (AES-NI)
16 GB DDR4 ECC UDIMM
Memory Module Pre-installed
16 GB (16 GB x 1)
Total Memory Slots
Maximum Memory Capacity
64 GB (16 GB x 4)
– Please select Synology memory modules for optimum compatibility and reliability. Synology will not provide complete product warranty or technical support if non-Synology memory modules are used for memory expansion.
– For more information on the recommended memory configurations, visit here.
– Synology reserves the right to replace memory modules with the same or higher frequency based on suppliers product life cycle status. Rest assured that the compatibility and stability have been strictly verified with the same benchmark to ensure identical performance.
Maximum Drive Bays with Expansion Unit
40 (RX1217/RX1217RP x 2)
Compatible Drive Type
3.5″ SATA HDD
2.5″ SATA SSD
Maximum Single Volume Size
200 TB (32 GB RAM required, for RAID 5 or RAID 6 groups only)
Hot Swappable Drive
– Storage Pool and volume creation require all drives to be listed as compatible on the device models compatibility list.
– “Compatible drive type” indicates drives that have been tested to be compatible with Synology products. This term does not indicate the maximum connection speed of each drive bay.
– Each internal volume (may consist of multiple drives) is expandable up to 108 TB (with memory less than 32 GB) or 200 TB (with memory equal to or greater than 32 GB).
RJ-45 1GbE LAN Port
4 (with Link Aggregation / Failover support)
RJ-45 10GbE LAN Port
2 (with Link Aggregation / Failover support)
USB 3.2 Gen 1 Port
The USB 3.0 standard was renamed to USB 3.2 Gen 1 by the USB Implementers Forum (USB-IF) in 2019.
2 x Gen3 x8 slots (x8 link)
exFAT Access is purchased separately in Package Center.
Form Factor (RU)
Rack Installation Support
4-post 19″ rack (Synology Rail Kit – RKS1317)
The rail kit is sold separately
80 mm x 80 mm x 3 pcs