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Enterprise NAS with built-in service continuity engineered for data-intensive applications.
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)
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 allow them to 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.
The RS4021xs+ includes two PCIe slots for performance, networking, and storage upgrades enabling it to adapt to any business environment2.
Upgrade network bandwidth in minutes by 2x or more with Synologys range of 10GbE NICs.
Boost read/write IOPS by up to 16 times by enabling SSD cache via our Synology M.2 NVMe adapter cards and SNV3000 Series SSDs or by installing one or more 2.5 SAT5200 SSDs.
Quickly and easily scale up to 40 drives with two RX1217(RP) expansion units.
Keep disaster at bay
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.
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.
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.
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.
Engineered to handle intensive 24/7 workloads, Synology drives consistently deliver top-grade performance.
The RS4021xs+ runs Synology DiskStation Manager (DSM), the unified operating system equipped with applications and services designed specifically for businesses.
Public Cloud Integration
Back up and synchronize data easily between public cloud accounts and your NAS.
Virtual Machine Manager
Run various operating systems in isolated sandboxes. Seamlessly clone, store, and migrate virtual machines.
Synology Drive
Instantly access your NAS files across multiple devices whenever you want, wherever you are.
Central Management System
Conveniently manage your fleet of Synology NAS from a centralized console.
Security
Secure data with comprehensive built-in security tools to protect your devices against evolving threats.
Collaboration Suite
Satisfy all team collaboration needs behind the safety of your own private cloud with Synology Office, Calendar, and Chat.
At Synology, we are committed to product innovation and quality. The RS4021xs+ is backed by a 5-year limited warranty that includes technical support and hardware replacement services to maximize your return on investment.
CPU |
CPU Model | Intel Xeon D-1541 |
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| 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 |
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Storage |
Drive Bays | 16 |
| Maximum Drive Bays with Expansion Unit | 40 (RX1217/RX1217RP x 2) | |
| Compatible Drive Type* (See all supported drives) |
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| Maximum Single Volume Size* |
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| Hot Swappable Drive | ||
| Notes |
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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 |
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| Notes | exFAT Access is purchased separately 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 - RKS1317) | |
| Notes | The rail kit is sold separately | |
Others |
System Fan | 80 mm x 80 mm x 3 pcs |
| Fan Speed Mode |
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| 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 | |
| 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) |
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| British Thermal Unit | 497.14 BTU/hr (Access) 213.74 BTU/hr (HDD Hibernation) |
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| Notes |
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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 |
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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 |
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Optional Accessories |
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| Notes | All memory modules will operate at the maximum frequency specified by the CPU manufacturer. | |
