With both the SAS-2 and SAS-3 fabrics, you are encouraged to apply entire shelves to pools, so you can gain the benefits of No Single Point of Failure (NSPF) configurations, and striping across the maximum possible number of devices.
SAS-2 - The SAS-2 (Serial Attached SCSI 2.0) host bus adapter (HBA) is designed for the Oracle ZFS Storage Appliance with a standard chip set to support a high-density of target devices, up to 1024. You can daisy-chain SAS-2 disks to as many as 36 disk shelves for certain systems, for a total of 864 disks. The SAS-2 HBA has 2x4 (8 PHYs) or 4x4 port (16 PHYs) with each supporting 6 Gbit/s (SAS-2) devices. For more information about the SAS-2 HBA, see the hardware overview for your controller.
For supported disk shelf configurations, see Disk Shelf Configurations.
SAS-3 - The SAS-3 (Serial Attached SCSI 3.0) host bus adapter (HBA) increases speed to 12 Gbit/s and is capable of supporting up to 4095 devices. You can daisy-chain SAS-3 disks to as many as 48 disk shelves for certain systems, for a total of 1152 disks. The SAS-3 HBA is a low-profile, 4x4 port (16 PHYs), with each port supporting 12 Gbit/s (SAS-3) devices. For more information about the SAS-3 HBA, see the hardware overview for your controller.
For supported disk shelf configurations, see Disk Shelf Configurations.