Inferring SAS expander topology

[Dustin Wenz]

I'm working on a server that has 6 LSI SAS expanders connected to it. Two of them are throwing intermittent command errors and need some attention. Because the host only has four external 8088 ports, I know some of the expanders are chained through each other.

Before I can send parts for replacement, I need to determine if the two problematic expanders are either daisy-chained or directly connected to the host. On Linux, this is trivial; I would just browse the device topology in /sys/. However, this machine is running FreeBSD 10.3, and I am unable to find a way to do this. I have sg3_utils available, as well as any build-in FreeBSD tools. Using this software, is it possible to determine if a SAS expander is chained off of another?

	- .Dustin