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Synology Rackstation RS4021xs+ 16 bays NAS

Synology Rackstation RS4021xs+ 16 bays NAS

Synology Rackstation RS4021xs+ 16 bays NAS High-Performance Enterprise

The RS4021xs+ is a 16-bay enterprise NAS designed for data-intensive applications. Equipped with an 8-core Intel® Xeon® processor, 10GbE connectivity, and scalable storage, it offers exceptional performance, reliability and service continuity. Ideal for businesses handling large workloads and critical data, it includes advanced backup solutions and flexible expansion options.

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Jan 23 - Jan 26
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Description

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 RX1217RP

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 cache

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 RX1217RP/RX1217 expansion units.

The ultimate backup solutions — license-free

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 high-intensity workloads, Synology hard drives consistently deliver top-grade performance.

HDD

Enterprise Series 3.5″ SAS

SSD

Enterprise Series 2.5″ SATA
Enterprise Series M.2 NVMe

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

Secure data with comprehensive built-in security tools to protect your devices against evolving threats.

Public Cloud Integration

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

5-year warranty

At Synology, we are committed to product innovation and quality. Synology guarantees a robust and reliable data management experience with a 5-year limited warranty, providing responsive technical support and hardware replacement services to maximize your return on investment.

  • 1. Power button and indicator
  • 2. Alert Off Button
  • 3. Drive tray
  • 4. Drive status indicator
  • 5. PSU fan
  • 6. Power Port
  • 7. PSU Indicators & Alert Off Buttons
  • 8. Console port
  • 9. 1GbE/10GbE RJ-45 Ports
  • 10. USB 3.2 Ports
  • 11. Expansion port
  • 12. PCIe expansion slot
  • 13. Reset button

Hardware Specs

Hardware Specifications
CPUCPU ModelIntel Xeon D-1541
CPU Quantity1
CPU Core8
CPU Architecture64-bit
CPU Frequency2.1 (base) / 2.7 (turbo) GHz
Hardware Encryption EngineYes
MemorySystem Memory16 GB DDR4 ECC UDIMM
Memory Module Pre-installed16 GB (16 GB x 1)
Total Memory Slots4
Maximum Memory Capacity64 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.
StorageDrive Bays16
Maximum Drive Bays with Expansion Unit40 (RX1217 x 2)
Compatible Drive Type* (See all supported drives)
  • 3.5" SATA HDD
  • 2.5" SATA SSD
Hot Swappable Drive*Yes
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 PortsRJ-45 1GbE LAN Port4
RJ-45 10GbE LAN Port2
USB 3.2 Gen 1 Port*2
Expansion Port2
Expansion Port TypeInfiniband
NotesThe USB 3.0 standard was renamed to USB 3.2 Gen 1 by the USB Implementers Forum (USB-IF) in 2019.
PCIePCIe Expansion2 x Gen3 x8 slots (x8 link)
AppearanceForm Factor (RU)3U
Size (Height x Width x Depth)132.3 mm x 482 mm x 656.5 mm
Weight17.4 kg
Rack Installation Support*4-post 19" rack (Synology Rail Kit - RKS-02)
NotesThe rail kit is sold separately
OthersSystem Fan80 mm x 80 mm x 3 pcs
Fan Speed Mode
  • Full-Speed Mode
  • Cool Mode
  • Quiet Mode
Easy Replacement System FanYes
Power RecoveryYes
Noise Level*44.7 dB(A)
Scheduled Power On / OffYes
Wake on LAN / WANYes
Power Supply Unit / Adapter800 watts
550 watts*
Redundant Power SupplyYes
AC Input Power Voltage100 V to 240 V AC
Power Frequency50/60 Hz, Single Phase
Power Consumption145.79 watts (Access)
62.68 watts (HDD Hibernation)
British Thermal Unit497.14 BTU/hr (Access)
213.74 BTU/hr (HDD Hibernation)
Notes
  • Power supply specifications vary by hardware revision. An 800 W PSU is used in devices with serial numbers containing T2R (5th to 7th digits), while a 550 W PSU is in devices with ULR and VR4 serial numbers. 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%
TemperatureOperating Temperature0°C to 35°C (32°F to 95°F)
Storage Temperature-20°C to 60°C (-5°F to 140°F)
Relative Humidity5% to 95% RH
Certification
  • FCC
  • CE
  • BSMI
  • VCCI
  • RCM
  • EAC
  • CCC
  • KC
  • UL
Warranty5 Years
NotesThe warranty period starts from the purchase date as stated on your purchase receipt.
EnvironmentRoHS 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
  • Enterprise Series 3.5" SATA HDD: HAT5300 Series
  • Enterprise Series 2.5" SATA SSD: SAT5200 Series
  • M.2 SSD & 10GbE Combo Adapter Card: E10M20-T1
  • M.2 SSD Adapter Card: M2D20
  • 25GbE Network Interface Card: E25G30-F2
  • 10GbE Network Interface Card: E10G21-F2/E10G30-T2/E10G18-T1
  • Rail Kit Sliding: RKS-02
NotesAll memory modules will operate at the maximum frequency specified by the CPU manufacturer.

Software Specs

DSM Specifications
Storage ManagementMaximum Single Volume Size
  • 1 PB (64 GB memory required, for RAID 6 groups only)
  • 200 TB (32 GB memory required)
  • 108 TB
Maximum Internal Volume Number256
SSD Read/Write Cache (Determining cache size) Yes
SSD TRIMYes
RAID GroupYes
Supported RAID Type
  • RAID F1
  • Basic
  • JBOD
  • RAID 0
  • RAID 1
  • RAID 5
  • RAID 6
  • RAID 10
RAID Migration
  • Basic to RAID 1
  • Basic to RAID 5
  • RAID 1 to RAID 5
  • RAID 5 to RAID 6
Volume Expansion with Larger HDDs
  • RAID F1
  • RAID 1
  • RAID 5
  • RAID 6
  • RAID 10
Volume Expansion by Adding a HDD
  • RAID F1
  • JBOD
  • RAID 5
  • RAID 6
Global Hot Spare Supported RAID Type
  • RAID F1
  • RAID 1
  • RAID 5
  • RAID 6
  • RAID 10
Notes
  • Usable capacity for each volume will be lower than the maximum volume size and is dependent on the filesystem and the amount of system metadata stored.
  • When Peta Volume is enabled, validated services and packages are required. Please refer to this article for more information on limitations.
  • Actual maximum storage pool and volume sizes depend on drive sizes used, the number of drive bays available, and the RAID configuration.
  • Volumes over 108 TB require 32 GB of memory or more.
File SystemInternal Drives
  • Btrfs
  • ext4
External Drives
  • Btrfs
  • ext4
  • ext3
  • FAT
  • NTFS
  • HFS+
  • exFAT
NotesexFAT 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.
File ServicesFile Protocol
  • SMB
  • AFP
  • NFS
  • FTP
  • WebDAV
  • Rsync
Maximum Concurrent SMB/AFP/FTP Connections4,000
Maximum Concurrent SMB/AFP/FTP Connections (with RAM expansion)10,000
Windows Access Control List (ACL) IntegrationYes
NFS Kerberos AuthenticationYes
Notes
  • Regarding data concerning tests with RAM expansion, all memory slots are installed with the maximum capacity of supported RAM.
  • During testing, the maximum number of SSDs supported by this model is installed in a RAID 5 configuration.
  • The testing standard was based on the maximum number of concurrent connections supported by this model. During the testing, 25% of the connections were used to transfer files concurrently. The transfer process guaranteed that the connections were not interrupted; the minimum transfer speed was not guaranteed.
Account & Shared FolderMaximum Local User Accounts16,000
Maximum Local Groups512
Maximum Shared Folder512
Maximum Shared Folder Sync Tasks32
Hybrid ShareHybrid Share Folder Number15
Hyper BackupData & Folder BackupYes
Entire System BackupYes
NotesFull-system backup requires DSM 7.2 or later.
High AvailabilitySynology High AvailabilityYes
Log CenterSyslog Events per Second3,000
VirtualizationVMware ESXi 6.5 and VAAIYes
Windows Server 2016Yes
Windows Server 2019Yes
Windows Server 2022Yes
Citrix ReadyYes
OpenStackYes
General SpecificationsSupported ProtocolsSMB1 (CIFS), SMB2, SMB3, NFSv3, NFSv4, NFSv4.1, NFS Kerberized sessions, iSCSI, Fibre Channel, HTTP, HTTPs, FTP, SNMP, LDAP, CalDAV
Supported Browsers
  • Chrome
  • Firefox
  • Edge
  • Safari
Supported LanguageEnglish, Deutsch, Français, Italiano, Español, Dansk, Norsk, Svenska, Nederlands, Русский, Polski, Magyar, Português do Brasil, Português Europeu, Türkçe, Český, ภาษาไทย, 日本語, 한국어, 繁體中文, 简体中文
NotesFor an updated list of supported browser versions, check the DSM Technical Specifications.
Add-on Packages view the complete package list
Antivirus by McAfee (Trial)Yes
Central Management SystemYes
Synology ChatSuggested Maximum Users6,000
Suggested Concurrent Users500
NotesFor tested models with expandable memory, the maximum amount of RAM was installed.
Download StationMaximum Concurrent Download Tasks80
SAN ManagerMaximum iSCSI Target Number256
Maximum LUN512
LUN Clone/Snapshot, Windows ODXYes
NotesiSCSI Manager has been renamed to SAN Manager in DSM 7.0.
Synology MailPlus / MailPlus ServerFree Email Accounts5 (Additional accounts require purchase of licenses)
Suggested Maximum Users10,000
Suggested Concurrent Users2,000
Maximum Server Performance4,312,000 emails per day, approx. 131GB
Notes
  • Models with more than 4 bays were installed with two SSDs for SSD cache.
  • For tested models with expandable memory, the maximum amount of RAM was installed.
  • The performance of the mail system will slightly decrease in high-availability mode due to data synchronization between the two servers.
  • Functions that were enabled in all of the tests above: anti-spam, anti-virus, DNSBL, greylist, content scan, full-text search (English only).
Media ServerDLNA ComplianceYes
Synology PhotosFacial RecognitionYes
Object RecognitionYes
Snapshot ReplicationMaximum Snapshots per Shared Folder1,024
Maximum of System Snapshots65,536
Surveillance StationDefault Licenses2 (Additional cameras require purchase of licenses)
Suggested Maximum IP Cameras and Total FPS (H.264)
  • 720p: 285 channels, 8550 FPS
  • 1080p: 280 channels, 2800 FPS
  • 3M: 200 channels, 2000 FPS
  • 5M: 120 channels, 1200 FPS
  • 4K: 85 channels, 850 FPS
Suggested Maximum IP Cameras and Total FPS (H.265)
  • 720p: 420 channels, 12600 FPS
  • 1080p: 285 channels, 8550 FPS
  • 3M: 280 channels, 2800 FPS
  • 5M: 200 channels, 2000 FPS
  • 4K: 120 channels, 1200 FPS
Notes
  • Surveillance Station 9.1.3 or above is required to support the maximum IP cameras and FPS figures listed.
  • Performance figures are obtained from testing conducted with the device fully populated with drives, with their default memory configuration, and under a continuous recording setup. Actual system capabilities may vary based on configuration, drive performance, enabled features, and the presence of additional workloads.
  • Use NVR Selector to quickly find a suitable model based on your requirements.
  • The maximum number of camera stream outputs is 2 times the suggested maximum number of IP cameras.
Synology DriveRecommended Number of Concurrent Sync Clients2,000 (the number of connections that can be maintained when the recommended number of hosted files was reached)
Recommended Number of Hosted Files50,000,000 (applies to files indexed or hosted by Synology Drive. For file access through other standard protocols, refer to the File Services section above)
Notes
  • Exceeding the recommended numbers above will not block application operations, but may result in longer response time.
  • Utilizing SSD cache can significantly improve performance.
  • For tested models with expandable memory, the maximum amount of RAM was installed.
  • Btrfs file system and non-encrypted shared folders were used during the aforementioned testing.
Synology OfficeSuggested Maximum Users12,500
Suggested Concurrent Users5,000
Notes
  • Multiple files were opened for testing and each file was edited by 30 users simultaneously.
  • For tested models with expandable memory, the maximum amount of RAM was installed.
  • Client performance may affect maximum simultaneous editing users. Client PCs used for testing: Intel Core i3-3220 / 8GB RAM
Video StationYes
Virtual Machine ManagerRecommended Virtual Machine Instances16
Recommended Virtual DSM Number (Licenses required) 16 (including 1 Free License)
NotesThe specifications vary depending on system configuration and memory size.
VPN ServerMaximum Connections60
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