Synology DiskStation DS1821+ NAS Review

DSM Specifications

Storage Management

Maximum Internal Volume Number 64 SSD Read / Write Cache (White Paper) 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

File Protocol SMB/AFP/NFS/FTP/WebDAV 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

Maximum Local User Accounts 2,048 Maximum Local Groups 256 Maximum Shared Folder 512 Maximum Shared Folder Sync Tasks 16

High Availability

Synology High Availability

Log Center

Syslog Events per Second 800

Virtualization

VMware vSphere with VAAI Windows Server 2016 Windows Server 2019 Citrix Ready OpenStack

General Specifications

Networking Protocols SMB1 (CIFS), SMB2, SMB3, NFSv3, NFSv4, NFSv4.1, NFS Kerberized sessions, iSCSI, HTTP, HTTPs, FTP, SNMP, LDAP, CalDAV Supported Browsers

Google Chrome
Firefox
Microsoft Edge
Internet Explorer 11 onwards
Safari 13 onwards
Safari (iOS 13.0 onwards)
Google Chrome (Android 11.0 onwards)

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

Add-on Packages view the complete package list

Antivirus by McAfee (Trial)

Central Management System

Synology Chat

Maximum Users 1,500 Notes

The number of concurrent HTTP connections for Synology Chat was configured to the maximum.
For tested models with expandable memory, the maximum amount of RAM was installed.

Document Viewer

Download Station

Maximum Concurrent Download Tasks 80

exFAT Access (Optional)

iSCSI Manager

Maximum iSCSI Target Number 128 Maximum iSCSI LUN 256 iSCSI LUN Clone/Snapshot, Windows ODX

Synology MailPlus / MailPlus Server

Free Email Accounts 5 (Licenses required for additional accounts) Maximum Number of Concurrent Users 150 Maximum Server Performance 1,484,000 emails per day, approx. 45GB 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 Server

DLNA Compliance

Moments

Facial Recognition Subject Recognition Auto Color & Rotate Moments Select

Snapshot Replication

Maximum Snapshots per Shared Folder 1,024 Maximum of System Snapshots 65,536

Surveillance Station

Maximum IP cam (Licenses required) 40 (including 2 Free License) (See All Supported IP Cameras) Total FPS (H.264) 1200 FPS @ 720p (1280×720)
1050 FPS @ 1080p (1920×1080)
600 FPS @ 3M (2048×1536)
440 FPS @ 5M (2591×1944)
320 FPS @ 4K (3840×2160) Total FPS (H.265) 1200 FPS @ 720p (1280×720)
1200 FPS @ 1080p (1920×1080)
1120 FPS @ 3M (2048×1536)
600 FPS @ 5M (2591×1944)
480 FPS @ 4K (3840×2160) Notes

Surveillance Station throughput is tested with Axis network camera, using continuous recording with live view from Surveillance Station and motion detection by camera. Live view and recording are sharing the same stream from the camera.
The maximum channel number also includes devices installed on Virtual DSM.
Total FPS may be affected by other services running at the same time (e.g., archive tasks performed by Archive Vault).

Synology Drive

Recommended 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) Recommended Number of Concurrent Sync Clients 550 (the number of connections that can be maintained when the recommended number of hosted files was reached) 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 Office

Maximum Users 1,800 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