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.

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CPUAMD Ryzen^™
Quad-core 2.2 GHz

Cache AccelerationDual M.2 2280 slots for NVMe Cache

Performance113K 4K random read IOPS

ScalabilityExpand up to 18 drives
with two DX517 expansion units

The performance you need

Reduce transfer times with the DS1821+, designed to accelerate your workloads. Easily add faster networking and NVMe drives to further boost performance.

The DS1821+ achieves up to 2,323 MB/s read and 1,460 MB/s write speeds

This device can be configured with up to 25GbE networking

The DS1821+ features two M.2 NVMe slots for caching or storage pool creation

Storage that fits your needs

Make the most of high-performance networking and file access without taking up unnecessary space. DS1821+ comes equipped with 8 bays and can scale up to 18 bays with 2 DX517 expansion units as your data needs grow.

It supports up to 300 TB of storage capacity after expansion when using 16 TB drives in a RAID 5 configuration

Fully certified storage virtualization solutions

Synology iSCSI storage fully supports most virtualization solutions to enhance work efficiency with easy management interface. VMware vSphere 6 and VAAI integration helps offload storage operations and optimizes computation efficiency. Windows Offloaded Data Transfer (ODX) speeds up data transfer and migration rate. OpenStack Cinder support turns your Synology NAS into a block-based storage component.

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.

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

Protect corporate data stored on the cloud. On-premise backup solution with a centralized dashboard. Optimize storage efficiency with single instancing and block-level deduplication technology.

Microsoft 365 Google Workspace

Extra protection with Extended Warranty Plus

Extend the standard 3-year hardware warranty of your DS1821+ with 2 more years of Synology-certified support and premium services that help you recover faster in the event of disaster.

Powered by Synology DiskStation Manager

Central Management System

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

Learn more

Synology MailPlus

Secure, reliable, and private mail server solution with an intuitive and modern mail client.

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Synology High Availability

Seamless transition between clustered servers in the event of a server failure to minimize the impact on applications.

Learn more

Security

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

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Synology Drive

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

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Surveillance Station

Complete surveillance solution for recording, monitoring, and management.

Learn more

Works best with Synology drives

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

HDD

Enterprise Series 3.5" SATA

Plus Series 3.5" SATA

SSD

Enterprise Series 2.5" SATA

Enterprise Series M.2 NVMe

Hardware Overview

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

Notes:Performance figures are achieved in the Synology lab with optimized network and configuration settings. Actual performance could vary in different environments. Comparison done against prior-generation 8-bay DS1819+. For full details on the test setup, please visit the Synology performance page here.Performance figures are obtained through SMB sequential throughput tests using Windows Server 2016 Datacenter on a DS1821+ with a Synology 10GbE NIC and SSD. Actual performance may vary depending on the testing environment, usage, and configuration. See performance charts for more information.PCIe add-in cards, expansion units, and storage drives are sold separately. Refer to the compatibility list for compatible devices.Synology SNV3400 series M.2 NVMe SSD drives can be installed through the built-in M.2 slots to enable SSD caching or create SSD storage pools. Drives are sold separately.Storage figure calculated based on a RAID 5 configuration. Total storage capacity may vary depending on hard drives used and RAID configuration.

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)
	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.
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 BIS
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	DDR4 ECC SODIMM: D4ES01-4G/D4ES01-8G/D4ECSO-2666-16G Expansion Units: DX517 Enterprise Series 3.5" SATA HDD: HAT5300 Series Plus Series 3.5" SATA HDD: HAT3300 Series Enterprise Series 2.5" SATA SSD: SAT5200 Series Enterprise Series M.2 2280 NVMe SSD: SNV3400 Series 25GbE Network Interface Card: E25G30-F2 10GbE Network Interface Card: E10G30-F2/E10G30-T2/E10G18-T1
	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	Data & Folder 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
	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 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). Models with expandable memory are tested with their maximum supported memory. To estimate the RAM requirement for your NAS, please read this article.
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)	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)	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 number of streams that can be viewed simultaneously is twice the suggested maximum number of cameras. For example, if the suggested maximum number of cameras for a model is 10 under H.264, 1080p, the model can support up to 20 streams of the same specification at the same time.
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

Notes: Model specifications are subject to change without prior notice. The figures are based on Synology internal testing. Each performance test is done individually. No other services or applications are processed at the same time. The actual performance may be lower than lab testing figure due to differences in server configuration, deployment, and the number of active operations. If usage requirements exceed the specifications above, please contact our regional partners for professional advice.