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
![](mob_102.png)
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.
![](mob_103.png)
When the front 24SFF bays are populated, any installed rear 2SFF drives are always 25 and 27.
![](mob_098.png)
If a 2SFF drive cage is connected to SAS expander port 3, then the drive numbers are 1 and 3.
Universal media bay
![](mob_096.png)
8LFF front panel
![](mob_042.png)
12LFF front panel
![4 LFF device bay numbering](mob_076.png)
Midplane box (LFF only)
![](mob_097.png)
Front 12LFF + Midplane 4LFF + All rear 2SFF
![](mob_149.png)