Ultimate Backup Solution
DS1821+ integrates various backup applications into an intuitive user interface, offering durable storage technologies to safeguard your valuable data on any device.
Quad-core 2.2 GHz
with two DX517 expansion units
Active Backup for Business
Centralize backup tasks for VMware, Windows, and file servers. Restore whatever you want fast and reliably when needed.
Learn more
Hyper Backup
Comprehensively back up your data to a local shared folder, an external device, another Synology NAS, an rsync server, or a public cloud to ensure data safety.
Learn more
Synology Drive
Safeguard your computer with Synology Drive Client. Effortlessly perform real-time data backups and point-in-time file recovery.
Learn more
Active Backup for Microsoft 365 / Google Workspace
On-premise backup solution with a centralized dashboard. Optimize storage efficiency with single instancing and block-level deduplication technology.
Microsoft 365Google WorkspacePowered by Synology DiskStation Manager
Central Management System
Conveniently manage your fleet of Synology NAS from a centralized console.
Synology MailPlus
Secure, reliable, and private mail server solution with an intuitive and modern mail client.
Synology High Availability
Seamless transition between clustered servers in the event of a server failure to minimize the impact on applications.
Security
Secure data with comprehensive built-in security tools to protect your devices against evolving threats.
Synology Drive
Instantly access your NAS files across multiple devices whenever you want, wherever you are.
Surveillance Station
Complete surveillance solution for recording, monitoring, and management.
Works best with Synology drives
Engineered to handle intensive 24/7 workloads, Synology drives consistently deliver top-grade performance.
HDD
SSD
- 1Status indicator
- 2Alert indicator
- 3Power button and indicator
- 4LAN indicator
- 5Drive status indicator
- 6Drive tray
- 7Drive tray lock
- 8USB 3.2 Gen 1 port
- 9Power port
- 10System fan
- 11PCIe expansion slot
- 12Kensington Security Slot
- 13Expansion port
- 141GbE RJ-45 port
- 15Reset button
- 16USB 3.2 Gen 1 port
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Hardware Specifications
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CPU
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CPU
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CPU Model | AMD Ryzen V1500B |
| CPU Quantity | 1 | |
| CPU Cores | 4 | |
| CPU Threads | 8 | |
| CPU Architecture | 64-bit | |
| CPU Frequency | 2.2 GHz | |
| Hardware Encryption Engine | ||
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Memory
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Memory
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System Memory | 4 GB DDR4 ECC SODIMM |
| Total Memory Slots | 2 | |
| Maximum Memory Capacity | 32 GB (16 GB x 2) | |
| Notes |
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Storage
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Storage
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Drive Bays | 8 |
| Maximum Drive Bays with Expansion Unit | 18 (DX517 x 2) | |
| M.2 Drive Slots | 2 (NVMe) | |
| Drive Type (See all supported drives) |
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| Hot Swappable Drive* | ||
| Notes | The hot swappable drive feature is not supported by M.2 SSD slots. | |
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External Ports
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External Ports
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RJ-45 1GbE LAN Port | 4 |
| USB 3.2 Gen 1 Port | 4 | |
| Expansion Port | 2 | |
| Expansion Port Type | eSATA | |
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PCIe
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PCIe
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PCIe Expansion | 1 x Gen3 x8 slot (x4 link) |
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Appearance
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Appearance
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Size (Height x Width x Depth) | 166 mm x 343 mm x 243 mm |
| Weight | 6 kg | |
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Others
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Others
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System Fan | 120 mm x 120 mm x 2 pcs |
| Fan Speed Mode |
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| Easy Replacement System Fan | ||
| Brightness Adjustable Front LED Indicators | ||
| Power Recovery | ||
| Noise Level* | 22.2 dB(A) | |
| Scheduled Power On / Off | ||
| Wake on LAN / WAN | ||
| Power Supply Unit / Adapter | 250 watts | |
| AC Input Power Voltage | 100V to 240V AC | |
| Power Frequency | 50/60 Hz, Single Phase | |
| Power Consumption |
59.8 watts (Access) 26.18 watts (HDD Hibernation) |
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| British Thermal Unit |
204.05 BTU/hr (Access) 89.33 BTU/hr (HDD Hibernation) |
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| Notes |
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Temperature
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Temperature
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Operating Temperature | 0°C to 40°C (32°F to 104°F) |
| Storage Temperature | -20°C to 60°C (-5°F to 140°F) | |
| Operating Humidity | 8% to 80% RH | |
| Storage Humidity | 5% to 95% RH | |
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Certification
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Certification
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Warranty
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Warranty
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2 Years | |
| Notes | The warranty period starts from the purchase date as stated on your purchase receipt. (Learn more) | |
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Environment
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Environment
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RoHS Compliant | |
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Packaging Content
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Packaging Content
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Optional Accessories
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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. | |
| Compatibility | Synology Compatibility List | |
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DSM Specifications
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| Maximum Single Volume Size | 108 TB | |
| Maximum Internal Volume Number | 64 | |
| M.2 SSD Storage Pool Support* | ||
| SSD Read/Write Cache (Determining cache size) | ||
| SSD TRIM | ||
| Supported RAID Type |
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| RAID Migration |
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| Volume Expansion with Larger HDDs |
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| Volume Expansion by Adding a HDD |
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| Global Hot Spare Supported RAID Type |
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| Notes |
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| Internal Drives |
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| External Drives |
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| File Protocol |
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| Maximum Number of SMB Connections (FSCT-Based) | 60 | |
| Windows Access Control List (ACL) Integration | ||
| NFS Kerberos Authentication | ||
| Notes |
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| Maximum Local User Accounts | 1,024 | |
| Maximum Local Groups | 256 | |
| Maximum Shared Folder | 256 | |
| Maximum Shared Folder Sync Tasks | 8 | |
| Hybrid Share Folder Number | 10 | |
| Data & Folder Backup | ||
| Entire System Backup | ||
| Notes | Full-system backup requires DSM 7.2 or later. | |
| Synology High Availability | ||
| Syslog Events per Second | 1,000 | |
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Virtualization
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Virtualization
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VMware vSphere | ESXi 8.0 U2, ESXi 8.0 U1, ESXi 8.0, ESXi 7.0 U3, ESXi 7.0 U2, ESXi 7.0 U1, ESXi 7.0, ESXi 6.7 U3, ESXi 6.7 U2, ESXi 6.7 U1, ESXi 6.7, ESXi 6.5 U3, ESXi 6.5 U2, ESXi 6.5 U1, ESXi 6.5 |
| Microsoft Hyper-V | Windows Server 2022, Windows Server 2019, Windows Server 2016 | |
| Citrix XenServer | XenServer 8, Citrix Hypervisor 8.2 LTSR CU1 | |
| OpenStack | Cinder | |
| Supported Protocols | SMB1 (CIFS), SMB2, SMB3, NFSv3, NFSv4, NFSv4.1, NFS Kerberized sessions, iSCSI, HTTP, HTTPs, FTP, SNMP, LDAP, CalDAV | |
| Supported Browsers |
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| Supported Language | English, 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 | |
| Notes | For an updated list of supported browser versions, check the DSM Technical Specifications. | |
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Add-on Packages view the complete package list
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Synology AI Console
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Synology AI Console
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Third-Party AI Model Integration | |
| Maximum De-Identification Rate | 60 words per second | |
| Notes |
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| Maximum Number of Users | 150 | |
| Notes |
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Download Station
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Download Station
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Maximum Concurrent Download Tasks | 80 |
| Maximum iSCSI Target Number | 64 | |
| Maximum LUN | 128 | |
| LUN Clone/Snapshot, Windows ODX | ||
| Free Email Accounts | 5 (Additional accounts require purchase of licenses) | |
| Maximum Number of Users | 130 | |
| Notes |
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| DLNA Compliance | ||
| Facial Recognition | ||
| Object Recognition | ||
| Maximum Snapshots per Shared Folder | 256 | |
| Maximum Snapshots per LUN | 64 | |
| Maximum Snapshots per System | 4,096 | |
| Maximum Replication Tasks for Shared Folders | 32 | |
| Maximum Replication Tasks for LUNs | 16 | |
| Maximum Replication Tasks per System | 32 | |
| Default Licenses | 2 (Additional cameras require purchase of licenses) | |
| Maximum IP Cameras and Total FPS (H.264) |
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| Maximum IP Cameras and Total FPS (H.265) |
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| Notes |
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| Maximum Number of Users | 110 | |
| Maximum Number of Hosted Files | 1,000,000 (applies to files indexed or hosted by Synology Drive. For file access through other standard protocols, refer to the File Services section above) | |
| Notes |
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| Maximum Number of Users | 110 | |
| Notes |
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| Recommended Virtual Machine Instances | 8 (Learn more) | |
| Recommended Virtual DSM Number (Licenses required) | 8 (including 1 Free License) | |
| Notes | The specifications vary depending on system configuration and memory size. | |
| Maximum Connections | 8 | |