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DiskStation® DS1821+

High capacity storage and data protection for anyone

Designed for scalability and performance

The 8-bay Synology DS1821+ is aimed at IT enthusiast and SMB customers looking for a powerful and scalable storage solution, its business-grade backup solutions keep users safe and protected from potential data loss, while major improvements to compute capabilities and throughput means workloads are finished faster than ever before. 

CPU

AMD Ryzen™ Quad-core 2.2 GHz

Cache Acceleration

Dual M.2 2280 slots for NVMe Cache

Performance

113K 4K random read IOPS1

Scalable

Expand up to 18 drives with two DX517 expansion units

Hardware Specifications
CPU
CPU
 CPU Model AMD Ryzen V1500B
CPU Quantity 1
CPU Core 4
CPU Architecture 64-bit
CPU Frequency 2.2 GHz
Hardware Encryption Engine
Memory
Memory
 System Memory 4 GB DDR4 ECC SODIMM
Memory Module Pre-installed 4 GB (4 GB x 1)
Total Memory Slots 2
Maximum Memory Capacity 32 GB (16 GB x 2)
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
Storage
 Drive Bays 8
Maximum Drive Bays with Expansion Unit 18 (DX517 x 2)
M.2 Drive Slots 2 (NVMe)
Compatible Drive Type* (See all supported drives)
  • 3.5" SATA HDD
  • 2.5" SATA HDD
  • 2.5" SATA SSD
  • M.2 2280 NVMe SSD
Hot Swappable Drive*
Notes
  • The hot swappable drive feature is not supported by M.2 SSD slots.
  • "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
External Ports
 RJ-45 1GbE LAN Port 4
USB 3.2 Gen 1 Port* 4
Expansion Port 2
Expansion Port Type eSATA
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
 PCIe Expansion 1 x Gen3 x8 slot (x4 link)
Appearance
Appearance
 Size (Height x Width x Depth) 166 mm x 343 mm x 243 mm
Weight 6 kg
Others
Others
 System Fan 120 mm x 120 mm x 2 pcs
Fan Speed Mode
  • Full-Speed Mode
  • Cool Mode
  • Quiet Mode
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)
British Thermal Unit 204.05 BTU/hr (Access)
89.33 BTU/hr (HDD Hibernation)
Notes
  • Power consumption is measured when it is fully loaded with Western Digital 1TB WD10EFRX 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
Temperature
 Operating Temperature 0°C to 40°C (32°F to 104°F)
Storage Temperature -20°C to 60°C (-5°F to 140°F)
Relative Humidity 5% to 95% RH
Certification
Certification
  • FCC
  • CE
  • BSMI
  • VCCI
  • RCM
  • EAC
  • CCC
  • KC
Warranty
Warranty
 3-year hardware warranty, extendable to 5 years with Extended Warranty Plus
Notes
  • The warranty period starts from the purchase date as stated on your purchase receipt. (Learn more)
  • Extended Warranty Plus is only available in Europe and North America. Refer to the Extended Warranty Plus website for details on supported countries/regions. (Learn more)
Environment
Environment
 RoHS Compliant
Packaging Content
Packaging Content
  • Main Unit X 1
  • Accessory Pack X 1
  • AC Power Cord X 1
  • RJ-45 LAN Cable X 2
  • Quick Installation Guide X 1
Optional Accessories
Optional Accessories
Notes All memory modules will operate at the maximum frequency specified by the CPU manufacturer.
DSM Specifications
Storage Management
Storage Management
 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
  • Synology Hybrid RAID
  • 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
  • Synology Hybrid RAID
  • RAID 1
  • RAID 5
  • RAID 6
  • RAID 10
Volume Expansion by Adding a HDD
  • Synology Hybrid RAID
  • JBOD
  • RAID 5
  • RAID 6
Global Hot Spare Supported RAID Type
  • Synology Hybrid RAID
  • RAID 1
  • RAID 5
  • RAID 6
  • RAID 10
Notes
  • Creating M.2 storage pools requires the use of Synology-verified SSDs, which are rigorously tested under extreme temperature conditions. Thermal parameters for SSDs and NAS units are fine-tuned to ensure optimal management of thermal conditions under I/O-intensive environments. (Learn more)
  • 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.
  • Each internal volume (may consist of multiple drives) is expandable up to 108TB.
File System
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.
File Services
File Services
 File Protocol
  • SMB
  • AFP
  • NFS
  • FTP
  • WebDAV
  • Rsync
Maximum Concurrent SMB/AFP/FTP Connections 1,000
Maximum Concurrent SMB/AFP/FTP Connections (with RAM expansion) 2,000
Windows Access Control List (ACL) Integration
NFS Kerberos Authentication
Notes
  • Regarding data concerning tests with RAM expansion, all memory slots are installed with the maximum capacity of supported RAM.
  • 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 Folder
Account & Shared Folder
 Maximum Local User Accounts 2,048
Maximum Local Groups 256
Maximum Shared Folder 512
Maximum Shared Folder Sync Tasks 16
Hybrid Share
Hybrid Share
 Hybrid Share Folder Number 10
Hyper Backup
Hyper Backup
 Folder and Package Backup
Entire System Backup
Notes Full-system backup requires DSM 7.2 or later.
High Availability
High Availability
 Synology High Availability
Log Center
Log Center
Log Center
 Syslog Events per Second 1,000
Virtualization
Virtualization
 VMware ESXi 6.5 and VAAI
Windows Server 2016
Windows Server 2019
Windows Server 2022
Citrix Ready
OpenStack
General Specifications
General Specifications
 Supported Protocols SMB1 (CIFS), SMB2, SMB3, NFSv3, NFSv4, NFSv4.1, NFS Kerberized sessions, iSCSI, HTTP, HTTPs, FTP, SNMP, LDAP, CalDAV
Supported Browsers
  • Chrome
  • Firefox
  • Edge
  • Safari
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.
Add-on Packages view the complete package list
Central Management System
Central Management System
Synology Chat
Synology Chat
Synology Chat
 Suggested Users 150
Notes Models with expandable memory are tested with their maximum supported memory.
Download Station
Download Station
Download Station
 Maximum Concurrent Download Tasks 80
SAN Manager
SAN Manager
SAN Manager
 Maximum iSCSI Target Number 128
Maximum LUN 256
LUN Clone/Snapshot, Windows ODX
Notes iSCSI Manager has been renamed to SAN Manager in DSM 7.0.
Synology MailPlus / MailPlus Server
Synology MailPlus / MailPlus Server
Synology MailPlus / MailPlus Server
 Free Email Accounts 5 (Additional accounts require purchase of licenses)
Suggested Users 750
Maximum Server Performance 1,484,000 emails per day, approx. 45GB
Notes
  • Suggested users is derived from testing in an environment with 20% heavy users (each with 20,000 pre-populated emails and receiving 240 emails per day) and 80% light users (each receiving an average of 20 emails per day). Learn more
  • Models with more than 4 bays were installed with two SSDs for SSD cache.
  • Models with expandable memory are tested with their maximum supported memory.
  • 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 Server
Media Server
Media Server
 DLNA Compliance
Synology Photos
Synology Photos
Synology Photos
 Facial Recognition
Object Recognition
Snapshot Replication
Snapshot Replication
Snapshot Replication
 Maximum Snapshots per Shared Folder 1,024
Maximum of System Snapshots 65,536
Surveillance Station
Surveillance Station
Surveillance Station
 Default Licenses 2 (Additional cameras require purchase of licenses)
Suggested Maximum IP Cameras and Total FPS (H.264)
  • 720p: 40 channels, 1200 FPS
  • 1080p: 40 channels, 1050 FPS
  • 3M: 40 channels, 600 FPS
  • 5M: 40 channels, 440 FPS
  • 4K: 32 channels, 320 FPS
Suggested Maximum IP Cameras and Total FPS (H.265)
  • 720p: 40 channels, 1200 FPS
  • 1080p: 40 channels, 1200 FPS
  • 3M: 40 channels, 1120 FPS
  • 5M: 40 channels, 600 FPS
  • 4K: 40 channels, 480 FPS
Notes
  • 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 Drive
Synology Drive
Synology Drive
 Recommended Number of Concurrent Sync Clients 550 (the number of connections that can be maintained when the recommended number of hosted files was reached)
Recommended Number of Hosted Files 50,000,000 (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.
  • Models with expandable memory are tested with their maximum supported memory.
  • Btrfs file system and non-encrypted shared folders were used during the aforementioned testing.
Synology Office
Synology Office
Synology Office
 Suggested Users 4,500
Notes
  • Suggested users is derived from testing in an environment with 60% idle users (each logging in and viewing documents) and 40% active users (each executing random actions at intervals of 20 to 40 seconds) operating within documents, each document having 30 users. Learn more
  • Models with expandable memory are tested with their maximum supported memory.
  • Client performance may affect maximum simultaneous editing users. Client PCs used for testing: Intel Core i3-3220 / 8GB RAM
Virtual Machine Manager
Virtual Machine Manager
Virtual Machine Manager
 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.
VPN Server
VPN Server
VPN Server
 Maximum Connections 40
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