The Synology FX2421 is a high-density 24-bay 2U all-flash expansion unit designed for seamless storage scalability with Synology FlashStation systems including the FS6400. Supporting both 2.5" SAS and SATA SSDs with hot-swappable drive bays, this expansion unit delivers rapid storage expansion or serves as a dedicated, rapidly accessible local backup destination. Features dual SAS ports (one input, one output) for high-speed connectivity with included expansion cable, enabling maximum data throughput and minimum latency as if drives were installed directly on the FlashStation. Built with dual redundant power supplies and hot-swappable system fans for maximum service uptime and easy component replacement. Plug-and-play design requires no additional software configuration for immediate use when connected to any Synology FlashStation. Optimized for use with Synology SAT5200 SATA SSDs, rigorously tested for proven interoperability and high reliability, delivering up to 67,000 4K random write IOPS and enterprise-grade endurance at 1.3 DWPD. Modularized components and hot-swappable drive trays ensure easy maintenance and maximum service availability. Optional RKS1317 sliding rail kit available for quick and secure rack cabinet installation. Ideal for expanding all-flash storage capacity in I/O-intensive environments including virtual machines, databases, and multimedia post-production workflows. Includes accessory pack, two AC power cords, and expansion cable. Backed by Synology's 5-year limited warranty with hardware replacement and technical support.