sporadic CAM (all devices) outage on 11-stable, mps(4), ahci(4) and bhyve(8) involved.

[Harry Schmalzbauer]

 Bezüglich Kevin Day's Nachricht vom 09.12.2016 16:34 (localtime):
> I’m not sure if this is related, but after upgrading from 10.x to 11.0-RELEASE we’re seeing on multiple systems that “camcontrol rescan all” causes all devices to detach in a similar fashion. All mps and achi drives timeout and/or just immediately disappear, then reattach. Interestingly mpr backed drives do not disappear.

I'm post r309273, but maybe this solves your problem:
https://svnweb.freebsd.org/changeset/base/309273

Best,

-harry