Synology RackStation RS4021xs+ 16-Bay Xeon D-1541 Scalable NAS Diskless

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.

Compute

Intel® Xeon® D-1541 8-core 2.1 GHz

Networking

Built-in dual-port 10GbE

Memory

16 GB ECC DDR4 Up to 64 GB

Scalability

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.

Redundant power

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.

Customize to your business

The RS4021xs+ includes two PCIe slots for performance, networking, and storage upgrades enabling it to adapt to any business environment2.

Double bandwidth

Upgrade network bandwidth in minutes by 2x or more with Synology’s range of 10GbE NICs.

SSD cache3

Boost read/write IOPS by up to 16 times by enabling SSD cache with our Synology M.2 NVMe adapter cards and SNV3500 SSDs, or by installing one or more 2.5” SAT5200 SSDs.

Storage expansion

Quickly and easily scale up to 40 drives with two RX1217(RP) expansion units.

The ultimate backup solutions — license-free

Hyper Backup

A comprehensive backup and recovery solution for securing data stored on Synology servers. Backup data locally, to another Synology device, rsync server, or cloud-based storage such as Google Drive, Dropbox, S3-compatible destinations, and Synology C2. Deduplication4, integrity checks, and incremental transfer technology reduce bandwidth and storage used.

Snapshot Replication

Easily schedule flexible point-in-time backups of shared folders and iSCSI LUNs with an RPO as low as 5 minutes and recovery in seconds. Set up replication and failover to other Synology storage systems for fast RTOs and minimal service disruption.

Active Backup Suite

Enables administrators to easily backup the entire IT infrastructure to their NAS, including Windows & Linux workstations and servers, file servers, VMware and Hyper-V virtual machines, and Microsoft 365 and Google Workspace accounts. Backups benefit from deduplication, multiversioning, and optimizations to reduce bandwidth and storage used.

Storage for virtualization

Synology iSCSI storage supports mainstream virtualization solutions with an easy management interface to enhance usability. VMware vSphere 6.5 and VAAI integration helps offload storage operations. Windows Offloaded Data Transfer (ODX) speeds up data transfer. OpenStack Cinder support turns your Synology NAS into a block-based storage component. Additionally, Synology Storage Console enables even more simplified storage provisioning and management options in VMware and Windows environments.

All-in-one surveillance solution

Synology Surveillance Station transforms the RS4021xs+ into a feature-packed Network Video Recorder solution. Support for up to 90 IP cameras5 and video analytics such as motion detection, no idle zone, foreign object detection, and anomaly detection cater to the most common surveillance scenarios.

Secure and private

AES-256 encryption keeps locally-stored footage secure.

Access from anywhere, anytime

Access recordings and live streams whenever you want using a web browser, desktop client, or the DS cam mobile app.

Real-time alerts

Email, SMS, or push notifications alert you when incidents occur or predefined conditions are met.

Works best with Synology drives

Engineered to handle intensive 24/7 workloads, Synology drives consistently deliver top-grade performance.

Powered by Synology DiskStation Manager

The RS4021xs+ runs Synology DiskStation Manager (DSM), the web-based operating system equipped with powerful applications and services for business.

Central Management System

Conveniently manage your fleet of Synology NAS from a centralized console.

Synology Drive

Instantly access your NAS files across multiple devices whenever you want, wherever you are.

Collaboration Suite

Satisfy all team collaboration needs behind the safety of your own private cloud with Synology Office, Calendar, and Chat.

Virtual Machine Manager

Run various operating systems in isolated sandboxes. Seamlessly clone, store, and migrate virtual machines.

Security

Shield your Synology NAS from the most sophisticated threats with industry-leading security solutions.

Public Cloud Integration

Back up and synchronize data easily between public cloud accounts and your NAS.

Specifications

Hardware Specs

CPU · CPU Model · Intel Xeon D-1541

CPU Quantity · 1

CPU Architecture · 64-bit

CPU Frequency · 8-core 2.1 (base) / 2.7 (turbo) GHz

Hardware Encryption Engine (AES-NI) · ✓

Memory · System Memory · 16 GB DDR4 ECC UDIMM

Memory Module Pre-installed · 16 GB (16 GB x 1)

Total Memory Slots · 4

Maximum Memory Capacity · 64 GB (16 GB x 4)

Notes

• Synology reserves the right to replace memory modules with the same or higher frequency based on supplier's product life cycle status. Rest assured that the compatibility and stability have been strictly verified with the same benchmark to ensure identical performance.
• 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 about the recommended memory configurations, please check the Hardware Installation Guide of your Synology product.

Storage

Drive Bays

16

Maximum Drive Bays with Expansion Unit · 40 (RX1217/RX1217RP x 2)

Compatible Drive Type* (See all supported drives)

• 3.5" SATA HDD
• 2.5" SATA SSD

Hot Swappable Drive* · ✓

Notes

• Synology only guarantees full functionality, reliability, and performance for Synology drives listed on the compatibility list. The use of non-validated components may limit certain functionality and result in data loss and system instability.
• "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.

External Ports

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* · 2

Expansion Port · 2

Notes · The USB 3.0 standard was renamed to USB 3.2 Gen 1 by the USB Implementers Forum (USB-IF) in 2019.

PCIe

PCIe Expansion

2 x Gen3 x8 slots (x8 link)

File System

Internal Drives

• Btrfs
• EXT4

External Drives

• Btrfs
• EXT4
• EXT3
• FAT
• NTFS
• HFS+
• exFAT

Notes · exFAT Access can be installed for free from Package Center in DSM 7.0. In DSM 6.2 or earlier versions, exFAT Access needs to be purchased in Package Center.

Appearance

Form Factor (RU)

3U

Size (Height x Width x Depth) · 132.3 mm x 482 mm x 656.5 mm

Weight · 17.4 kg

Rack Installation Support* · 4-post 19" rack (Synology Rail Kit - RKS-02)

Notes · The rail kit is sold separately

Others

System Fan

80 mm x 80 mm x 3 pcs

Fan Speed Mode

• Full-Speed Mode
• Cool Mode
• Quiet Mode

Easy Replacement System Fan · ✓

Power Recovery · ✓

Noise Level* · 44.7 dB(A)

Scheduled Power On / Off · ✓

Wake on LAN / WAN · ✓

Power Supply Unit / Adapter

800 W
550 W

Redundant Power Supply · ✓

AC Input Power Voltage · 100 V to 240 V AC

Power Frequency · 50/60 Hz, Single Phase

Power Consumption

145.79 W (Access)
62.68 W (HDD Hibernation)

British Thermal Unit

497.14 BTU/hr (Access)
213.74 BTU/hr (HDD Hibernation)

Notes

• Power supply specifications may differ based on the hardware revision of the device. For more information, refer to the Product Change Notice.
• Power consumption is measured when it is fully loaded with Synology 8TB HAT5300-8T hard drive(s).
• Noise Level Testing Environment: Fully loaded with Seagate 2TB ST2000VN000 hard drive(s) in the idle state. Two G.R.A.S. Type 40AE microphones, each set up 1 meter away from the Synology NAS at the front and rear. Background noise: 16.49-17.51 dB(A); Temperature: 24.25-25.75˚C; Humidity: 58.2-61.8%

Temperature

Operating Temperature

0°C to 35°C (32°F to 95°F)

Storage Temperature · -20°C to 60°C (-5°F to 140°F)

Relative Humidity · 5% to 95% RH

Certification

• FCC
• CE
• BSMI
• VCCI
• RCM
• EAC
• CCC
• KC
• UL

Warranty

5 Years

Notes · The warranty period starts from the purchase date as stated on your purchase receipt. (Learn more)

Environment

RoHS Compliant

Packaging Content

• Main Unit X 1
• Accessory Pack X 1
• AC Power Cord X 2
• Quick Installation Guide X 1

Optional Accessories

• DDR4 ECC UDIMM: D4EC-2666-16G
• Expansion Units: RX1217/RX1217RP
• 3.5" SATA HDD: HAT5300
• 2.5" SATA SSD: SAT5210
• M.2 SSD & 10GbE Combo Adapter Card: E10M20-T1
• M.2 SSD Adapter Card: M2D20
• 25GbE Network Interface Card: E25G21-F2
• 10GbE Network Interface Card: E10G21-F2/E10G18-T2/E10G18-T1
• Rail Kit Sliding: RKS-02
• Surveillance Device License Pack

Notes · All memory modules will operate at the maximum frequency specified by the CPU manufacturer.