Drive bay numbering: SAS expander

Drive numbering through a SAS Expander is continuous:

  • SAS expander port 1 always connects to port 1 of the controller.
  • SAS expander port 2 always connects to port 2 of the controller.
  • SAS expander port 3 = drive numbers 1 to 4.
  • SAS expander port 4 = drive numbers 5 to 8.
  • SAS expander port 5 = drive numbers 9 to 12.
  • SAS expander port 6 = drive numbers 13 to 16.
  • SAS expander port 7 = drive numbers 17 to 20.
  • SAS expander port 8 = drive numbers 21 to 24.
  • SAS expander port 9 = drive numbers 25 to 28.

Common configuration examples:

NVMe drives



When any stacked 2SFF drive cage is connected to the SAS expander, the drive numbering skips the second number to allow uFF drive bay numbering. For example, when a rear 2SFF drive cage is connected to SAS expander port 9, then the drive numbers are 25 and 27.



When the front 24SFF bays are populated, any installed rear 2SFF drives are always 25 and 27.



If a 2SFF drive cage is connected to SAS expander port 3, then the drive numbers are 1 and 3.

Universal media bay



8LFF front panel



12LFF front panel


4 LFF device bay numbering

Midplane box (LFF only)



Front 12LFF + Midplane 4LFF + All rear 2SFF