camcontrol sata affiliations

[David Ford]

> -----Original Message-----
> From: asomers at gmail.com [mailto:asomers at gmail.com] On Behalf Of Alan Somers
> Sent: 16 February 2016 15:23
> To: David Ford <david.ford at ouce.ox.ac.uk>
> Cc: freebsd-scsi at freebsd.org
> Subject: Re: camcontrol sata affiliations
>
> You aren't missing anything.  This is just a difference between SATA
> and SAS.  SAS drives have two ports, and SATA drives have only one.
> Most (all?) multipath JBODs like yours have two separate expander
> chips.  They connect every slot's first port to the first expander and
> every slot's second port to the second expander.  That results in a
> chassis with no SPOF.  With such hardware, there's no way to connect a
> SATA drive to both servers.  And with more complicated hardware that
> uses a single expander chip combined with SAS zoning to connect a SATA
> drive to two servers, you're stuck with a SPOF.

Thanks that at least clarifies what's going on. I had understood most of that, 
however I thought that the idea of the ability to clear the affiliation 
was to permit the second expander to take over. I suspect I was mistaken.

Thanks

David