Synology Expansion Unit FX2421
Synology Expansion Unit FX2421
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Synology Expansion Unit FX2421

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On-the-Fly Storage Capacity Expansion for Synology FlashStation
Synology FX2421 expansion units for Synology FlashStation1 make it easy to upgrade your allflash storage space with Synology enterprise SSD. Each 2U rackmount unit lets you add 24 additional 2.5” drive bays on the fly using an expansion cable. Synology FX2421 is the first 24 bay expansion unit to support Synology’s SAT5200 SATA SSD, allowing you to create a highly reliable and integrated storage setup, and receive long-term Synology updates and support. Synology FX2421 is backed by Synology’s 5-year limited warranty. 


  • Seamless Storage Expansion
24 additional drive bays available for online volume
expansion on the fly for your Synology FlashStation1
  • Best Fit With Enterprise-Grade Synology SSD
Use with Synology SAT5200 SATA SSD for high
performance, endurance, and verified compatibility
  • High-Reliability Design
Modularized components including redundant power
supplies and system fans ensure maximum uptime
  • Easy Hardware Setup
Plug-and-play design and fast rack fixing lock support
make upgrading storage space easy

Technical Specifications

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 Drive Bays 24

Compatible Drive Type* (See all supported drives) 2.5" SAS HDD
2.5" SAS SSD

Maximum Internal Raw Capacity 92.16 TB (3.84 TB drive x 24) (Capacity may vary by RAID types)

Hot Swappable Drive*

RAID Management through Synology DSM

Notes It is strongly recommended that you only install drives listed on your device's compatibility list. Storage pool and volume creation processes may fail when using unverified drives. Synology is unable to provide technical support for devices using unsupported components.
"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 SAS IN-port 1

SAS OUT-port 1
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 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 (for RP model)

Notes Power consumption is measured when it is fully loaded with HGST 1.8TB HUC101818CS4204 hard drive(s).
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 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 UL