problems with SAS JBODs 2

[Oliver Sech]

> 1) Are the expanders daisy chained?  Some SAS expanders don't work reliably
> when daisy chained.   Best to direct connect each one to the server.
At the moment I have 1 JBOD connected to 1 HBA Port with 1 cable (4 lanes?).
Unfortunately the JBOD has 24 slots in the front and 20 in the back and, those are connected via a internal SAS daisy chaining.
I could rewire and connect each backplane directly to the server, but unfortunately I do not have enough ports..

JOBD Model: Supermicro 847E2C-R1K28JBOD

> 2) Are the expanders connected in multipath or single path?  You need
> geom_multipath if you're going to do that.
See answer 1. There is a single path from the host to the first expander.

> 3) Are you attempting to use wide ports (two SAS cables connecting each
> expander to the HBA).  If do, you'll need to make sure that each pair of
> SAS cables goes to the same HBA chip (not merely the same card, as some
> cards contain two HBA chips).
see 1. The last time I opened one of those JBODs there were 8 SAS cables between the Front and Back expander. I assume that wide ports are being used.
(2 expanders per backplane as well)

> 4) Are you trying to remove an expander while ZFS is active on that
> expander?  That will suspend your pool, and ZFS doesn't always recover from
> a suspended state.
I'm testing with a new unused disk shelf that was never part of the ZFS pool. There were