Synology FX2421 Expansion Unit Rackmount 24 bays (2.5″ SAS/SATA drives)


Synology FX2421 Expansion Unit Rackmount 24 bays (2.5″ SAS/SATA drives)

Expand your FlashStation1 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 FlashStation. FX2421 expansion units can also be used as a dedicated and rapidly accessible local backup destination. The FX2421 expansion units for FlashStation1 make it easy to upgrade your all-flash storage space.
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 SAT5200 SATA SSD, allowing you to create a highly reliable and integrated storage setup, and receive long-term updates and support.

• 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 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
• Extended After-Sales Support


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SKU: FX2421 Category:
tech brand


Applied Models

Supports creating volumes across different units
  • FS series:FS6400, FS3600, FS3400
  • Expansion Unit FX2421 can only be used with identical expansion units.
  • DSM version requirement: 6.2.3-25426-2 or later version.
  • 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.


Drive Bays 24
Compatible Drive Type* (See all supported drives)
  • 2.5″ SAS HDD
  • 2.5″ SAS SSD
  • 2.5″ SATA 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 “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


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 – RKS1317)
Notes The rail kit is sold separately


Power Supply Unit / Adapter 500 W
AC Input Power Voltage 100 V to 240 V 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).


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


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%




5 Years
Notes The warranty period starts from the purchase date as stated on your purchase receipt. (Learn more)

Environment & Packaging


RoHS Compliant

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

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