The Synology RX2417sas is a 24-bay SAS/SATA expansion chassis designed to easily add additional storage capacity to the Synology FlashStation or Rackstation providing on-the-fly volume expansion or as a backup target. It has dual power supplies and hot swappable drive trays.
Supports creating volumes across different units:
Storage enclosure - 24 bays (SATA-600 / SAS) - SAS (external) - rack-mountable - 2U - P/N RX2417SAS