Synology
Synology DS1821+ 8 Bay NAS DiskStation (Diskless)
★★★★★
4K
An 8-bay NAS powerhouse with M.2 cache slots and expansion to 18 drives for growing data needs.
$1,031.17*
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*Price sourced from Amazon.com. Last updated:Jul 14, 2026.Price and availability are subject to change.
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Overview
Key Features
Accelerated Performance - 177% higher 4K random read IOPS and 76% faster sequential write speeds compared to its predecessor
Maximize Performance - Turbocharge HDD arrays by 20x or more without occupying drive bays using dual built-in M.2 slots for NVMe SSD cache
Expansion Made Easy - Scale-up on-demand to 18 drives with two DX517 expansion units
Includes Everything to Protect Your Data - Back up critical data to and from public clouds, Windows PCs and servers, virtual machines, and data on the NAS with Synology Active Backup suite, Hyper Backup, and Snapshot Replication
Ready for 10GbE - Add in a 10GbE SFP+ or RJ-45 NIC to instantly increase network bandwidth based on your existing infrastructure
Specifications
Brand
Synology
Model
DS1821+
Number of Bays
8 (expandable to 18 with 2x DX517)
RAM
4 GB DDR4
M.2 Slots
2x NVMe (SSD cache)
Expansion Slot
PCIe 3.0 (10GbE NIC ready)
Hard Drive Interface
SATA
Hard Drive Type
3.5" / 2.5" (sold separately)
Hardware Platform
PC
Pros & Cons
👍 Pros
- Eight drive bays with expansion to 18 drives via DX517 units provide substantial scalability
- Dual built-in M.2 NVMe slots enable SSD caching without sacrificing any drive bays
- PCIe slot supports optional 10GbE networking for high-bandwidth environments
- Comprehensive free backup software suite covers cloud, PC, server, and VM protection
- Significantly faster 4K random read and sequential write performance over the previous generation
👎 Cons
- Sold diskless, so the total cost increases substantially once drives are purchased
- Ships with only 4 GB of DDR4 RAM, which may require an upgrade for memory-intensive workloads
- DX517 expansion units are an additional expense and are not included
- No built-in 10GbE port; the NIC must be purchased and installed separately
- Fan and drive noise can be noticeable in a quiet home or office environment
Frequently Asked Questions
Does the DS1821+ come with hard drives included?
No, the DS1821+ is sold diskless. You will need to purchase compatible 3.5" or 2.5" SATA drives separately and install them yourself.
Can I add 10 Gigabit Ethernet to the DS1821+?
Yes, the DS1821+ has a PCIe expansion slot that accepts a 10GbE NIC in either SFP+ or RJ-45 configuration, allowing you to upgrade network bandwidth based on your infrastructure.
What are the two M.2 slots used for?
The two built-in M.2 NVMe slots are dedicated to SSD caching, which can dramatically accelerate random read/write performance on HDD arrays without occupying any of the eight main drive bays.
How far can I expand storage beyond the eight built-in bays?
By connecting up to two Synology DX517 expansion units, you can scale the DS1821+ to a total of 18 drives, adding capacity on demand as your storage requirements grow.
What backup solutions are included with the DS1821+?
Synology includes Active Backup Suite, Hyper Backup, and Snapshot Replication at no additional cost, supporting backups to and from public clouds, Windows PCs, servers, and virtual machines.
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