Synology 12-Bay DiskStation Expansion Unit Alternatives: 6 Similar Picks Compared
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You might be looking for synology 12 bay expansion unit alternatives if the Synology DX1215II does not fit your exact needs. This diskless unit adds twelve SATA drive bays to your existing Synology NAS. It measures 17.1 inches wide and weighs 19.9 pounds. The design prioritizes verified compatibility and plug-and-play upgrades. However, you may need a standalone system with its own processor and RAM. Some users prefer rackmount chassis for data centers. Others want built-in NVMe cache or faster network ports.
The 6 alternatives on this list share the twelve-bay capacity of the original. They overlap in form factor or drive count but offer different specs. You can choose an Asustor rackmount model for virtualization support. A QNAP or Asustor NAS provides dual 2.5GbE ports for higher throughput. The Synology DS2422+ includes a quad-core processor for better performance scaling. Each option serves a specific use case. You should compare the dimensions, RAM, and connectivity to find the right fit.
Our top pick: Synology 12-Bay DiskStation Expansion Unit.
How alternatives compare to DX1215II
Asustor Lockerstor 4-Bay Quad-Core NAS
The Asustor AS6604T is a self-contained NAS rather than an expansion unit. It offers four drive bays instead of twelve, so you lose raw capacity. It makes up for this with M.2 NVMe slots and dual 2.5GbE ports. The original DX1215II relies on your main NAS for processing and networking. This Asustor model includes a quad-core processor and 4GB of RAM. It is a better choice if you need local caching and faster network throughput. It suits users who do not need twelve bays but want high performance in a smaller 6.69-inch wide chassis.
QNAP 4-Bay 10GbE SFP+ NAS
The QNAP TS-431X3 is a compact four-bay NAS focused on network speed. It provides 10GbE and 2.5GbE connectivity, which exceeds the expansion unit's reliance on your host NAS's ports. You give up eight drive bays and massive storage density. This unit weighs just 5.1 pounds and measures 10 inches on each side. It is ideal for users who prioritize high throughput over raw capacity. The DX1215II is for those adding storage to an existing system. Pick this QNAP if you need a small footprint with enterprise-grade networking speeds for a smaller setup.
Asustor Lockerstor 12-Bay Rackmount NAS
The Asustor AS6512RD is a 12-bay rackmount NAS, matching the bay count of the DX1215II. Unlike the diskless expansion unit, this is a complete standalone system. It includes a quad-core processor and 8GB of RAM for better performance. It supports rackmount installation, which the original does not. You gain processing power and virtualization support but lose the simple plug-and-play expansion feature. It is heavier at 25.8 pounds and measures 17.3 inches wide. Choose this if you need dense storage with built-in computing power in a rack environment.
Synology 12-Bay Quad-Core NAS
The Synology DS2422+ is a 12-bay NAS that matches the bay count of the DX1215II. It is a complete system with a quad-core processor and 4GB of RAM. The original is diskless and relies on your main NAS. This Synology model offers higher throughput and independent operation. It weighs 20.9 pounds and measures 17 inches wide. You gain performance and flexibility but lose the simplicity of adding bays to an existing unit. It suits users who want to manage drive installation for better scaling. Pick this if you need a powerful standalone NAS with twelve bays.
Synology 12-Bay Xeon Desktop Enclosure
The Synology DS3622xs+ is a 12-bay enterprise NAS with 16GB of RAM. It matches the bay count of the DX1215II but provides significantly more memory. It is a standalone system with a Xeon processor, unlike the diskless expansion unit. It weighs 21.6 pounds and measures 18.3 inches wide. You gain enterprise-grade speed for virtualization and backups. You lose the simple expansion capability. This unit is for users who need scalable storage and robust processing power. Choose it if you require high performance for enterprise tasks rather than just adding drive bays.
BUFFALO TeraStation 51220RH 12-Bay 240TB
The BUFFALO TS51220RH is a 12-bay rackmount NAS with 240TB of pre-installed storage. It matches the bay count but includes drives and 10GbE connectivity. The DX1215II is diskless and requires your own drives and host NAS. This BUFFALO unit weighs 55.4 pounds and measures 29 inches long. It is a ready-to-use solution for businesses needing high capacity and security. You gain immediate storage and enterprise features. You lose the flexibility of expanding an existing Synology system. Pick this if you need a complete, high-capacity rackmount solution with drives included.
Quick picks
Our 7 picks
Synology 12-Bay DiskStation Expansion Unit
Best for: expanding Synology NAS with SATA drives
- Drive Bays
- 12-Bay
- Included Storage
- Diskless
- Dimensions
- 18.5 × 17.1 × 16.5 inches
- Weight
- 19.9 pounds
View on Amazon: Synology 12-Bay DiskStation Expansion Unit Affiliate link
The Synology DX1215II is a 12-bay diskless expansion unit designed to add storage capacity to your existing Synology NAS. It features a plug-and-play setup for easy upgrades and supports Synology HAT5300 SATA HDDs for verified compatibility. Measuring 270 x 300 x 340 mm and weighing 19.9 pounds, it offers a compact footprint for dense storage configurations.
Pros
- Provides 12 additional drive bays for expanded storage
- Plug-and-play design simplifies the upgrade process
- Verified compatibility with Synology HAT5300 SATA HDDs
- Backed by a 5-year limited warranty
Cons
- Diskless design requires an existing Synology NAS host
- No internal power supply included in the unit
- Limited to SATA drives, not suitable for all-flash needs
Good fit if
- You need to scale storage on an existing Synology NAS
- You prefer verified drive compatibility for reliability
- You want a simple plug-and-play expansion solution
Skip if
- You need a standalone NAS without a host unit
- You require an all-flash storage configuration
- You are looking for a unit with built-in power redundancy
Verdict: Synology DX1215II 12-Bay Expansion Unit is ideal for users expanding their Synology NAS with high-capacity SATA drives. It fits those prioritizing verified compatibility and easy integration over standalone performance.
Asustor Lockerstor 4-Bay Quad-Core NAS
Best for: users needing NVMe cache and dual 2.5GbE
- Drive Bays
- 4-Bay
- Network Connectivity
- 2x 2.5GbE
- Processor
- Quad-Core 2.0GHz
- RAM Capacity
- 4GB DDR4
- M.2 NVMe Slots
- 2 slots
- Included Storage
- Diskless
View on Amazon: Asustor Lockerstor 4-Bay Quad-Core NAS Affiliate link
The Asustor Lockerstor 4 AS6604T is a 4-bay NAS with a Quad-Core 2.0GHz processor and 4GB DDR4 RAM. It features two 2.5GbE ports and two M.2 NVMe slots for cache expansion. This unit suits users needing fast local connectivity and SSD acceleration. It includes backup apps and free IP camera licenses. You get a compact 6.53-pound chassis with comprehensive software tools.
Pros
- Two M.2 NVMe slots for SSD cache
- Dual 2.5GbE network ports
- 4GB DDR4 RAM for multitasking
- Quad-Core 2.0GHz processor
- Includes four free IP camera licenses
Cons
- Only four drive bays
- No 10GbE network option
- No USB 3.2 Gen 2 ports listed
Good fit if
- You need NVMe cache for speed
- You want dual 2.5GbE connectivity
- You require four drive bays
Skip if
- You need twelve drive bays
- You require 10GbE networking
- You want a diskless expansion unit
Verdict: Asustor Lockerstor 4 AS6604T fits users who prioritize NVMe caching and dual 2.5GbE ports over high drive capacity. It is a capable mid-range NAS for those who do not need twelve bays.
QNAP 4-Bay 10GbE SFP+ NAS
Best for: High-speed small capacity storage
- Drive Bays
- 4-Bay
- Network Connectivity
- 1x 10GbE, 1x 2.5GbE, 1x 1GbE
- Processor
- AnnapurnaLabs AL-314
- RAM Capacity
- 4GB DDR3L
- Included Storage
- Diskless
- Dimensions
- 10 × 10 × 10 inches
View on Amazon: QNAP 4-Bay 10GbE SFP+ NAS Affiliate link
This QNAP NAS offers four drive bays for flexible storage expansion. It includes a quad-core 1.7GHz processor and 4GB of DDR3L memory. Network connectivity is strong with one 10GbE port, one 2.5GbE port, and one 1GbE port. The device is diskless, meaning you supply the drives. It suits users needing fast data transfer speeds without the bulk of a 12-bay system.
Pros
- Four 3.5-inch SATA drive bays
- Single 10GbE SFP+ port
- Single 2.5GbE port
- Quad-core 1.7GHz processor
- Expandable RAM up to 8GB
Cons
- Only four drive bays compared to 12-bay alternatives
- Diskless design requires separate drive purchase
- No 2.5G ports on some variants
Good fit if
- You need high-speed 10GbE connectivity
- You want a compact 4-bay solution
- You already own compatible hard drives
Skip if
- You require 12 drive bays
- You need pre-installed storage drives
- You prefer a 2.5G and 10G port configuration only
Verdict: QNAP 4-Bay NAS with 10GbE and 2.5GbE fits users who prioritize network speed over raw capacity. It is ideal for those needing a small footprint with high throughput.
Asustor Lockerstor 12-Bay Rackmount NAS
Best for: high-density rackmount storage
- Drive Bays
- 12 Bay
- Processor
- Intel Atom C3538
- RAM Capacity
- 8 GB DDR4-2133
- Included Storage
- Diskless
- Form Factor
- Rackmount
- Network Connectivity
- 5GbE, 2.5GbE
View on Amazon: Asustor Lockerstor 12-Bay Rackmount NAS Affiliate link
This 12-bay rackmount NAS uses an Intel Atom C3538 quad-core CPU at 2.1GHz. It includes 8GB of expandable DDR4 RAM and dual 2.5GbE ports for high-speed connectivity. The unit supports virtualization and Docker. It is designed for users needing significant storage capacity in a dense, professional form factor.
Pros
- 12 drive bays for high capacity
- Expandable RAM up to 128GB
- Dual 2.5GbE network ports
- Supports Docker and virtual machines
Cons
- Requires rackmount installation
- No 10GbE port included
- Heavier build at 25.8 pounds
Good fit if
- You need a high-density storage solution
- You have rack space available
- You require expandable RAM
Skip if
- You prefer a desktop form factor
- You need built-in 10GbE
- You want a lightweight unit
Verdict: Asustor 12-Bay Rackmount NAS fits users who need dense storage and virtualization support in a rackmount chassis.
Synology 12-Bay Quad-Core NAS
Best for: Users needing high throughput and expansion
- Drive Bays
- 12-Bay
- Processor
- Quad Core
- RAM Capacity
- 4GB DDR4
- Included Storage
- Diskless
- Dimensions
- 18.5 × 17 × 16.5 inches
- Weight
- 20.9 pounds
View on Amazon: Synology 12-Bay Quad-Core NAS Affiliate link
The Synology DS2422+ is a 12-bay diskless NAS with a quad-core CPU and 4GB DDR4 RAM. It delivers up to 2,201 MB/s read speeds. You can expand capacity to 24 bays using a DX1222 unit. The unit supports up to 32 GB of memory and 10/25GbE networking. It weighs 20.9 pounds and includes a 3-year warranty.
Pros
- 12-bay diskless chassis design
- Up to 2,201 MB/s sequential read speed
- Expandable to 24 bays with DX1222
- Supports up to 32 GB RAM
Cons
- Only 4GB base RAM
- Diskless, requires separate drives
- No redundant power supply
Good fit if
- You need high sequential read speeds
- You plan to expand storage later
- You want a 3-year warranty
Skip if
- You need redundant power
- You want more than 12 bays
- You need pre-installed drives
Verdict: Synology DS2422+ 12-Bay NAS suits users needing high throughput and expansion flexibility. It fits those willing to manage drive installation for better performance scaling.
Synology 12-Bay Xeon Desktop Enclosure
Best for: Enterprise virtualization and backup systems
- Drive Bays
- 12-Bay
- Processor
- 6-core Intel Xeon
- Included Storage
- Diskless
- RAM Capacity
- 16GB RAM
- Dimensions
- 17 × 18.3 × 17 inches
- Weight
- 21.6 pounds
View on Amazon: Synology 12-Bay Xeon Desktop Enclosure Affiliate link
The Synology DS3622xs+ is a 12-bay diskless NAS built for heavy workloads. It features a 6-core Intel Xeon processor and 16GB of RAM. You get over 260,000 4K random read IOPS and up to 4,700 MB/s sequential read speeds. The unit supports up to 48GB memory and 10/25GbE networking. It scales to 36 bays with expansion units. This model suits users needing high performance and reliability.
Pros
- 6-core Intel Xeon processor
- 16GB RAM with 48GB max support
- Over 260,000 4K random read IOPS
- Up to 4,700 MB/s sequential read
Cons
- Diskless design requires separate drives
- Larger 17-inch height than desktop models
- No mention of NVMe SSD Cache4 in specs
Good fit if
- You need high IOPS for virtual machines
- You plan to expand to 36 bays
- You require 10/25GbE networking options
Skip if
- You want a pre-loaded drive system
- You need a compact desktop footprint
- You prefer a single-bay or 4-bay unit
Verdict: Synology DS3622xs+ 12-Bay Enterprise NAS delivers enterprise-grade speed for virtualization and backup systems. It fits users who need scalable storage and robust processing power.
BUFFALO TeraStation 51220RH 12-Bay 240TB
Best for: Businesses needing 240TB rackmount storage with drives
- Drive Bays
- 12-Bay
- Network Connectivity
- 10GbE
- Included Storage
- 240TB (12x20TB)
- RAID Support
- RAID 0, 6
- Form Factor
- Rackmount
- Dimensions
- 29 × 3.4 × 18.9 inches
View on Amazon: BUFFALO TeraStation 51220RH 12-Bay 240TB Affiliate link
This is a 12-bay rackmount NAS with 240TB of storage included. It features a native 10GbE port for fast transfers and 256-bit drive encryption. The system ships in RAID 6 for 200TB usable space. You get snapshots for ransomware recovery and cloud sync options. It includes a 5-year warranty with US support. This unit suits businesses needing high capacity and security in a rackmount form factor.
Pros
- 12 enterprise-grade hard drives included for 240TB total capacity
- Native 10GbE port for high-speed data transfers
- 256-bit drive encryption and two-factor authentication
- Snapshots for instant data recovery and ransomware mitigation
- 5-year warranty with 24/7 US-based support
Cons
- Rackmount form factor requires compatible server racks
- Heavier build at 55.4 pounds
- Closed system limits third-party app flexibility
Good fit if
- You need a fully populated 12-bay solution with drives included
- You require native 10GbE connectivity for fast transfers
- You want a rackmount unit with a 5-year warranty
Skip if
- You need a diskless expansion unit for existing drives
- You prefer a desktop form factor over rackmount
- You need more than 12 drive bays
Verdict: BUFFALO TeraStation 51220RH 12-Bay 240TB delivers high capacity and security for businesses needing a ready-to-use rackmount solution with 10GbE and a 5-year warranty.
Specifications side by side
| Spec | Synology 12-Bay DiskStation Expansion Unit | Asustor Lockerstor 4-Bay Quad-Core NAS | QNAP 4-Bay 10GbE SFP+ NAS | Asustor Lockerstor 12-Bay Rackmount NAS | Synology 12-Bay Quad-Core NAS | Synology 12-Bay Xeon Desktop Enclosure | BUFFALO TeraStation 51220RH 12-Bay 240TB |
|---|---|---|---|---|---|---|---|
| Drive Bays | 12-Bay | 4-Bay | 4-Bay | 12 Bay | 12-Bay | 12-Bay | 12-Bay |
| Network Connectivity | not stated | 2x 2.5GbE | 1x 10GbE, 1x 2.5GbE, 1x 1GbE | not stated | not stated | not stated | 10GbE |
| Processor | not stated | Quad-Core 2.0GHz | AnnapurnaLabs AL-314 | Intel Atom C3538 | Quad Core | 6-core Intel Xeon | not stated |
| RAM Capacity | not stated | 4GB DDR4 | 4GB DDR3L | 8 GB DDR4-2133 | 4GB DDR4 | not stated | not stated |
| M.2 NVMe Slots | not stated | 2 slots | not stated | not stated | not stated | not stated | not stated |
| Included Storage | Diskless | Diskless | Diskless | Diskless | Diskless | Diskless | 240TB (12x20TB) |
| RAID Support | not stated | not stated | not stated | not stated | not stated | not stated | RAID 0, 6 |
| Form Factor | not stated | not stated | not stated | Rackmount | not stated | not stated | Rackmount |
| Hardware Interface | not stated | M.2 NVMe | not stated | not stated | not stated | not stated | not stated |
| Number of Bays | 12-Bay | 4-Bay | 4-Bay | 12-Bay | 12-Bay | 12-Bay | 12-Bay |
| Processor Cores | not stated | Quad-Core | not stated | Quad-Core | Quad-Core | not stated | not stated |
| Dimensions | 18.5 × 17.1 × 16.5 inches | 9.06 × 6.69 × 7.3 inches | 10 × 10 × 10 inches | 21.1 × 17.3 × 3.46 inches | 18.5 × 17 × 16.5 inches | 17 × 18.3 × 17 inches | 29 × 3.4 × 18.9 inches |
| Weight | 19.9 pounds | 6.53 pounds | 5.1 pounds | 25.8 pounds | 20.9 pounds | 21.6 pounds | 55.4 pounds |
| Size | 270 mm x 300 mm x 340 mm | 4 Bay | 2.5GbE and 10GbE Ports | 5.5"(W) x 7.5"(H) x 9.1"(D) | 12-bay; 4GB DDR4 | DS3622xs+ | 240TB (12x20TB) |
| Color | Black | AS6604T | black | AS6512RD | Black | Black | Black |
| Model | DX1215II | AS6604T | TS-431X3 | AS6512RD | DS2422+ | DS3622xs+ | TS51220RH24012 |
Frequently asked questions
Can I use a 12-bay NAS instead of an expansion unit?
Yes, you can replace the expansion unit with a standalone 12-bay NAS. Models like the Synology DS2422+ or the Asustor AS6512RD offer full 12-bay capacity. These units operate independently rather than attaching to an existing system. They provide their own processing power and RAM. This approach is better if you need a complete, self-contained storage solution without relying on a primary NAS.
What is the difference between an expansion unit and a standalone NAS?
An expansion unit, such as the Synology DX1215II, adds drive bays to an existing Synology NAS. It has no internal processor or operating system. A standalone NAS, like the Asustor AS6604T, functions as a complete computer with its own CPU, RAM, and network ports. You choose an expansion unit for capacity growth and a standalone NAS for independent operation and features like NVMe caching.
Which 12-bay option offers the most RAM for virtualization?
The Synology DS3622xs+ provides 16GB of RAM, which is the highest capacity listed for 12-bay units. This amount of memory supports enterprise-grade virtualization and backup systems. Other 12-bay options like the DS2422+ and AS6512RD offer 4GB and 8GB respectively. If your workload requires heavy multitasking or multiple virtual machines, the 16GB configuration is the most capable choice for performance scaling.
Do I need a rackmount chassis for a 12-bay system?
Not necessarily, but rackmount models like the Asustor AS6512RD and BUFFALO TS51220RH are designed for server racks. They have a lower height, such as 3.46 inches for the Asustor, to fit standard 19-inch racks. Desktop units like the Synology DX1215II are taller and wider. Choose rackmount if you have limited floor space or need to mount equipment in a data center environment.
Can I get a 12-bay NAS with pre-installed drives?
Yes, the BUFFALO TeraStation 51220RH comes with 240TB of storage installed across twelve 20TB drives. This ready-to-use solution saves you the time of purchasing and installing individual drives. Other options like the Synology DS3622xs+ are sold as bare units. You must buy drives separately for those models. The BUFFALO option is ideal for businesses needing immediate, high-capacity deployment.
Which alternative supports M.2 NVMe caching?
The Asustor AS6604T supports M.2 NVMe drives for caching. Although it only has four bays, it includes dedicated slots for high-speed SSDs. This feature accelerates read and write operations for frequently accessed data. The 12-bay alternatives listed do not mention NVMe support in their specifications. If NVMe caching is critical, the 4-bay Asustor model is the only option that provides this hardware capability.
How do network speeds compare across these 12-bay units?
Network connectivity varies significantly. The BUFFALO TS51220RH and Synology DS3622xs+ do not list specific port speeds in the provided data, though the BUFFALO is noted for 10GbE. The Asustor AS6512RD and DS2422+ support 2.5GbE and 5GbE connections. The 4-bay QNAP TS-431X3 offers both 10GbE SFP+ and 2.5GbE ports. For high-throughput needs, check the specific port specifications of the standalone NAS models.
Is the Synology DX1215II compatible with all Synology NAS models?
The DX1215II is designed to expand specific Synology NAS systems. It is not a standalone computer and cannot function without a compatible host unit. You must verify your existing Synology model supports the DX1215II expansion. If your current NAS does not support this expansion unit, you must choose a standalone alternative like the Synology DS2422+ or a different brand entirely.