24-bay 2.5" expansion unit for Synology FlashStation

Expand your Synology FlashStation with Expansion Unit FX2421 for 24 additional 2.5” drive bays whenever needed. Without additional software configuration, FX2421 is immediately ready for use when connected to Synology FlashStation. FX2421 expansion units can also be used as a dedicated and rapidly accessible local backup destination.

Expand FlashStation with Synology SAT5200 SSD

Synology enterprise-grade SAT5200 SATA SSD, developed in tandem with FX2421, provides proven interoperability and high reliability through rigorous validation and compatibility testing with Synology expansion units. Combine SAT5200 drives with Synology FlashStation and FX2421 for a highly reliable and integrated storage setup, and receive long-term Synology updates and support. Learn more

Enterprise Series 2.5" SATA

High-performance data transmission

The high-speed expansion cable provided with FX2421 enables high bandwidth connectivity for maximum data throughput between your Synology FlashStation and Expansion Unit. Drives in FX2421 operate with minimum data latency, as if installed directly on your Synology FlashStation, allowing you to take advantage of high SSD I/O performance.

High-reliability design, easy hardware setup

The FX2421 is a highly reliable and thoroughly tested expansion unit that comes with hot-swappable drive trays and modularized components. Redundant power supplies and system fans can be replaced with ease to ensure maximum service uptime. The optional RKS1317 sliding rail kit provides fast rack fixing lock support for quick and secure rack cabinet installation.

5-year warranty

At Synology, we are committed to product innovation and quality. Synology guarantees a robust and reliable data management experience with a 5-year limited warranty, providing responsive technical support and hardware replacement services to maximize your return on investment.

Synology Replacement Service (SRS)

SRS provides free advance replacement units as early as the next business day in selected regions, maximizing the service uptime for your mission-critical storage and ensuring your business continuity. Learn more

Notes:

View specifications for a list of supported models.

Hardware Specifications
Applied Models
Applied Models	Supports creating volumes across different units	FS series:FS6400, FS3600, FS3400
	Notes	Expansion Unit FX2421 can only be used with identical expansion units. To have better performance, we recommend creating storage volumes physically located within the same NAS or Expansion Unit, rather than creating volumes across your NAS and Expansion Unit. DSM version requirement: 6.2.3-25426-2 or later version.
Storage
Storage	Drive Bays	24
	Compatible Drive Type* (See all supported drives)	2.5" SAS HDD 2.5" SAS SSD 2.5" SATA SSD
	Hot Swappable Drive*
	RAID Management through Synology DSM
	Notes	Synology only guarantees full functionality, reliability, and performance for Synology drives listed on the compatibility list. The use of non-validated components may limit certain functionality and result in data loss and system instability. "Compatible drive type" indicates drives that have been tested to be compatible with Synology products. This term does not indicate the maximum connection speed of each drive bay.
External Ports
External Ports	SAS IN-port	1
	SAS OUT-port	1
Appearance
Appearance	Size (Height x Width x Depth)	88 mm x 430.5 mm x 692 mm
	Size (Height x Width x Depth) (with server ears)	88 mm x 482 mm x 724 mm
	Weight	14.5 kg
	Rack Installation Support*	4-post 19" rack (Synology Rail Kit - RKS-02)
	Notes	The rail kit is sold separately
Power
Power	Power Supply Unit / Adapter	500 W
	AC Input Power Voltage	100V to 240V AC
	Power Frequency	50/60 Hz, Single Phase
	Power Consumption	190.99 W (Access)
	British Thermal Unit	651.68 BTU/hr (Access)
	Redundant Power Supply
	Notes	Power consumption is measured when it is fully loaded with HGST 1.8TB HUC101818CS4204 hard drive(s).
Temperature
Temperature	Operating Temperature	0°C to 35°C (32°F to 95°F)
	Storage Temperature	-20°C to 60°C (-5°F to 140°F)
	Relative Humidity	5% to 95% RH
Others
Others	System Fan	80 mm x 80 mm x 4 pcs
	Easy Replacement System Fan
	Noise Level*	57 dB(A)
	Notes	Noise Level Testing Environment: Fully loaded with Toshiba 600GB AL14SEB060N 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%
Certification
Certification	UL FCC CE EAC VCCI RCM KC
Warranty
Warranty	5 Years
	Notes	The warranty period starts from the purchase date as stated on your purchase receipt. (Learn more)
Environment & Packaging
Environment
Environment	RoHS Compliant
Packaging Content
Packaging Content	Main Unit X 1 Accessory Pack X 1 AC Power Cord X 2 Expansion Cable: MiniSAS-HD X 1 Quick Installation Guide X 1
Optional Accessories
Optional Accessories	Enterprise Series 2.5" SATA SSD: SAT5200 Series Rail Kit Sliding: RKS-02

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.