Taobao has many 2U hot-swap cages for sale with SAS expanders and daisy-chain capabilities. These are pulled from Inspur servers disposed by the reverse supply chain of hyperscalers.

A cottage industry of accessories and enclosures for these hot-swap cages has also sprung up around them.

TODO

• Bays: 12 × 3.5″ SAS3/SATA3
• Ports: 3 × SAS3 - Mini-SAS HD (SFF-8643) connectors
• Tray P/N: RM13919-01D (OEM: Chenbro)
• Expander chip: PMC Sierra PM8388 SXP 24x3G (24 ports - 12 connected to rear ports, 12 connected to drives)

• Daisy chain mode
  • Use any 1 × Mini-SAS HD connector as 4 × SAS wide link to HBA
  • Use any 1 × Mini-SAS HD connector as 4 × SAS wide link to downstream cages' expanders
• Passthrough mode
  • Connect all 3 × Mini-SAS HD connectors to HBA(s), all disks are passed through 1:1
  • If only (any) 2 × Mini-SAS HD connectors are connected to HBA(s), 4 × drive trays will be non-functional i.e. there is no support for 8:12 HBA:drive SAS links