So dual link is purely for the sake of redundancy and failover? I'm new to the SAS/Expander world and have read some about SAS multipathing but would like experts to confirm:If you are using SATA drives, I don't know if dual-linking the cards helps at all. SATA can only use a single channel as far as I remember. If you view the card in the MSM software, I think if you have dual links it only shows one up. I will have to check my systems again to be sure.
- Assume we have HBA1 and HBA2, both 8 channel with dual SFF-8087 ports and this Expander with 24 ports and 6x SFF-8087
- We have this particular expander, and is connected to both HBAs via single link, so HBA1 Port 1 -> EXP Port 1 and HBA2 Port 1 -> EXP Port 2
- now the EXP has 4x SFF-8087 left over which we'll connect to a backplane and populate with SAS drives
- Is the assumption now should either HBA1 or HBA2 goes down, the devices and software will automatically failover to the path provided by the other HBA?
- If both HBAs are up, do you get all the PCI-e bandwidth provided by both?
- What if the expander goes down? In a truly redundant case would you want 2 expanders and connect both HBAs to EXPs in a crisscrossed arrangement?