4-Bay vs 12-Bay NAS Devices in 2026: Key Differences
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You are comparing a 4-Bay vs 12-Bay NAS device from Synology and Asustor. Both units are diskless rackmount expansion or storage systems designed for server environments. They share a focus on expandability and management through dedicated operating systems. The main difference lies in their capacity and processing power. The Synology unit offers a compact 4-bay form factor, while the Asustor model provides a robust 12-bay chassis with a quad-core processor and significant RAM for heavy workloads.
Key differences
| Aspect | Synology 4-Bay Rackmount Expansion Unit | Asustor Lockerstor 12-Bay Rackmount NAS |
|---|---|---|
| Number of Bays | 4-Bay | 12-Bay |
| Processor | not listed | Intel Atom C3538 Quad-Core 2.1GHz |
| RAM Capacity | not listed | 8 GB DDR4-2133 (Expandable to 128GB) |
| Network Connectivity | not listed | 2x Gigabit + 2x 2.5GbE (5GbE aggregated) |
| Weight | 9.44 pounds | 25.8 pounds |
Which one should you choose?
Choose Synology 4-Bay Rackmount Expansion Unit if
- You need a compact, plug-and-play expansion unit for a 2-post or wall-mount rack.
- Your storage requirements are modest and you prefer a lightweight, energy-saving design.
- You already have a primary NAS and want to add 4 bays seamlessly via DSM.
Choose Asustor Lockerstor 12-Bay Rackmount NAS if
- You require high capacity with 12 drive bays for large datasets or virtualization.
- You need strong processing power with a quad-core CPU and up to 128GB of RAM.
- You plan to run Docker containers, virtual machines, or iSCSI targets simultaneously.
Verdict: The Synology RX418 is the better choice for users seeking a lightweight, easy-to-manage expansion unit for existing setups. The Asustor AS6512RD suits those who need a standalone, high-performance server with extensive RAM and network options. Your decision depends on whether you prioritize compact expansion or raw processing and storage capacity.
4-Bay vs 12-Bay NAS Comparison
Number of Bays
The Synology RX418 offers four drive bays. This unit is a diskless expansion unit designed to add storage to an existing Synology NAS. It focuses on expanding capacity without requiring a separate management system. The Asustor AS6512RD provides twelve drive bays. This is a standalone rackmount NAS with significant raw storage potential. It includes its own processing power and memory. If you need maximum drive count in a single chassis, the Asustor unit wins. If you are adding to an existing system, the Synology model is the correct choice for expansion.
RAM Capacity
The Asustor Lockerstor 12RD comes with 8 GB of DDR4-2133 RAM. This memory is expandable up to 128 GB using four 32 GB modules. This allows for heavy virtualization, Docker containers, and large cache operations. The Synology RX418 is an expansion unit. It does not have its own RAM capacity listed in the specifications. It relies on the host NAS for processing and memory tasks. For independent performance and multitasking, the Asustor unit has a clear advantage due to its substantial and upgradable memory.
Processor Cores
The Asustor AS6512RD features an Intel Atom C3538 quad-core processor running at 2.1 GHz. This CPU handles data management, virtual machines, and application services independently. The Synology RX418 is an expansion chassis. It does not list a processor in its specifications. It depends entirely on the connected Synology NAS for all computational tasks. If you need a device that processes data on its own, the Asustor model is superior. The Synology unit is a passive storage add-on without its own computing core.
Network Connectivity
The Asustor NAS includes two Gigabit Ethernet ports and two 2.5-Gigabit Ethernet ports. These can be aggregated to provide up to 5 Gbps of throughput. It also has a PCIe slot for adding a 10-Gigabit Ethernet card for even higher speeds. The Synology RX418 does not list network ports in its specifications. As an expansion unit, it connects via a proprietary cable to the main NAS, not directly to your network. For direct high-speed network access and aggregation, the Asustor unit offers significantly better connectivity options.
Physical Dimensions
The Synology RX418 measures 17 inches in length, 11.4 inches in width, and 1.73 inches in height. It weighs 9.44 pounds. This slim profile fits easily into 2-post racks. The Asustor AS6512RD measures 21.1 inches in length, 17.3 inches in width, and 3.46 inches in height. It weighs 25.8 pounds. The Asustor unit is larger and heavier due to its twelve bays and internal components. The Synology unit is more compact and lighter. If rack space is limited, the Synology model is smaller. If you need maximum capacity, the Asustor is larger.
Which NAS fits your needs
Existing Synology users expanding storage
The Synology RX418 is a diskless expansion unit designed to integrate seamlessly with your current Synology NAS. It allows for online volume expansion, letting you add four extra drive bays without downtime. This plug-and-play design helps you increase capacity quickly while managing everything through Synology DiskStation Manager. It is a practical choice for growing your existing infrastructure.
Businesses needing standalone server power
The Asustor AS6512RD is a complete 12-bay NAS with a Quad-Core 2.1GHz CPU and 8GB of DDR4 RAM. It supports virtual machines, Docker, and major enterprise platforms like VMware and Hyper-V. With dual 2.5GbE ports and a PCIe slot for 10GbE upgrades, it handles heavy workloads and complex business applications efficiently as a standalone server.
Users maximizing rack space efficiency
You get twelve drive bays in a 2U rackmount form factor with the Asustor AS6512RD. This density allows you to store significantly more data than the 4-bay Synology option. The unit includes robust networking options and memory for demanding tasks. It is ideal if you need high capacity and processing power in a compact, standardized rack space.
Quick picks
| # | Product | Best for | Price |
|---|---|---|---|
| 1 | Synology 4-Bay Rackmount Expansion Unit | expanding Synology NAS capacity | Check price of Synology 4-Bay Rackmount Expansion Unit on Amazon |
| 2 | Asustor Lockerstor 12-Bay Rackmount NAS | high-capacity rackmount storage needs | Check price of Asustor Lockerstor 12-Bay Rackmount NAS on Amazon |
The products compared
Synology 4-Bay Rackmount Expansion Unit
Best for: expanding Synology NAS capacity
- Number of Bays
- 4-Bay (what this guide is about)
- Drive Bays
- 4-Bay
- Included Storage
- Diskless
- Dimensions
- 17 × 11.4 × 1.73 inches
- Weight
- 9.44 pounds
View on Amazon: Synology 4-Bay Rackmount Expansion Unit Affiliate link
The Synology RX418 is a diskless 4-bay expansion unit designed to increase your NAS storage capacity. It connects seamlessly to your existing Synology system for online volume expansion. The unit measures 17 by 11.4 by 1.73 inches and weighs 9.44 pounds. It supports deep sleep mode for energy savings and is managed through Synology DiskStation Manager.
Pros
- 4-bay capacity for additional drive storage
- Plug-and-play online volume expansion
- Compact 12-inch depth fits 2-post racks
- Energy-saving deep sleep mode
Cons
- Diskless design requires separate drive purchase
- Limited to 4 bays compared to 12-bay options
- Requires existing Synology NAS for operation
Good fit if
- You need to expand existing Synology storage
- You have limited rack space available
- You want to add drives without replacing your main unit
Skip if
- You need a standalone NAS system
- You require more than 4 drive bays
- You do not own a Synology NAS
Verdict: Synology RX418 4-Bay Expansion Unit is a targeted storage add-on for Synology users needing more capacity without replacing their primary device. It fits well in tight rack spaces but offers no standalone functionality.
Asustor Lockerstor 12-Bay Rackmount NAS
Best for: high-capacity rackmount storage needs
- Number of Bays
- 12-Bay (what this guide is about)
- Drive Bays
- 12 Bay
- Processor
- Intel Atom C3538
- RAM Capacity
- 8 GB DDR4-2133
- Included Storage
- Diskless
- Form Factor
- Rackmount
View on Amazon: Asustor Lockerstor 12-Bay Rackmount NAS Affiliate link
This is a 12-bay rackmount NAS designed for high-density storage. It features a quad-core 2.1GHz CPU and 8GB of DDR4 RAM. The unit includes two Gigabit and two 2.5GbE ports for flexible networking. You can expand the RAM up to 128GB. It supports virtual machines and Docker applications. This device suits users who need substantial storage capacity in a server environment.
Pros
- 12 drive bays for large storage capacity
- Quad-core 2.1GHz Intel Atom C3538 processor
- 8GB DDR4 RAM expandable to 128GB
- 2.5GbE and Gigabit Ethernet ports
- Supports Docker and virtual machines
Cons
- Rackmount form factor requires server rack space
- 25.8 pounds weight makes it heavy to move
- Diskless design requires purchasing drives separately
Good fit if
- You need a high-capacity storage solution for a server rack
- You require expandable RAM for virtualization tasks
- You want 2.5GbE networking speeds
Skip if
- You need a compact desktop NAS for home use
- You prefer a pre-loaded storage device
- You have limited space for rackmount equipment
Verdict: Asustor 12-Bay Rackmount NAS is a robust option for users who need extensive storage and processing power in a rackmount form factor. It fits those building a dedicated server infrastructure.
Specifications side by side
| Spec | Synology 4-Bay Rackmount Expansion Unit | Asustor Lockerstor 12-Bay Rackmount NAS |
|---|---|---|
| Drive Bays | 4-Bay | 12 Bay |
| Processor | not stated | Intel Atom C3538 |
| RAM Capacity | not stated | 8 GB DDR4-2133 |
| Included Storage | Diskless | Diskless |
| Form Factor | not stated | Rackmount |
| Number of Bays | 4-Bay | 12-Bay |
| Network Connectivity | not stated | 5GbE, 2.5GbE |
| Processor Cores | not stated | Quad-Core |
| Dimensions | 17 × 11.4 × 1.73 inches | 21.1 × 17.3 × 3.46 inches |
| Weight | 9.44 pounds | 25.8 pounds |
| Size | 44 mm x 480 mm x 325 mm | 5.5"(W) x 7.5"(H) x 9.1"(D) |
| Color | black | AS6512RD |
| Model | RX418 | AS6512RD |
Frequently asked questions
Can a 4-bay NAS handle large video editing projects?
A 4-bay NAS like the Synology RX418 is designed primarily for expanding existing capacity rather than standalone heavy processing. It lacks independent functionality, meaning it relies on a primary NAS for data management. For large video projects, you need a robust main server, not just an expansion unit. This device adds four bays to your current setup without downtime, supporting your workflow indirectly.
Is a 12-bay NAS better for a home server?
A 12-bay NAS offers significant storage density and processing power, making it suitable for dedicated server infrastructure. The Asustor AS6512RD features a quad-core processor and 8GB of RAM, handling complex tasks efficiently. While powerful, its rackmount form factor and size may not fit typical home environments. It is best for users building a centralized, high-capacity storage solution in a dedicated space.
What is the size difference between 4-bay and 12-bay rackmount units?
The 12-bay Asustor AS6512RD is substantially larger than the 4-bay Synology RX418. The Asustor measures 21.1 inches in length and 17.3 inches in width, weighing 25.8 pounds. The Synology unit is smaller, at 17 inches long and 11.4 inches wide, weighing 9.44 pounds. You must ensure your rack space can accommodate the larger dimensions and weight of the 12-bay option.
Does a 4-bay expansion unit need its own operating system?
No, the Synology RX418 is a diskless expansion unit that does not run its own operating system. It is designed to integrate seamlessly with an existing Synology NAS, allowing for online volume expansion. You do not need to manage a separate system for this unit. It simply adds four drive bays to your current infrastructure, relying on the primary NAS for all management tasks.
How much RAM does a high-capacity 12-bay NAS typically have?
High-capacity 12-bay NAS devices often include substantial RAM to handle multiple concurrent tasks. The Asustor AS6512RD comes with 8GB of RAM, supporting its quad-core processor. This configuration helps manage heavy workloads and large datasets efficiently. More RAM ensures smoother performance when serving data to multiple users or running virtual machines alongside storage functions.
Can I use a 4-bay unit as a standalone NAS?
The Synology RX418 cannot function as a standalone NAS. It is specifically designed as a targeted storage add-on for Synology users. It offers no standalone functionality and requires a primary Synology device to operate. You must already own a compatible Synology NAS to utilize this expansion unit for additional capacity.
What network speeds do 12-bay rackmount NAS devices support?
The Asustor AS6512RD supports 5GbE and 2.5GbE network connectivity options. These speeds allow for faster data transfer compared to standard Gigabit connections, which is crucial for high-capacity environments. Faster networking ensures that the increased storage density does not become a bottleneck for data access. This makes the 12-bay unit suitable for demanding server infrastructures.