Unable to shutdown

[David Magda]

On Tue, August 30, 2011 11:50, Kevin Oberman wrote:
[...]
> The more I look at this, the more it seems to me that it is an issue
> with the Seagate drive and not a FreeBSD issue. Probably a bug that is
> never triggered on Windows, so is largely unnoticed. I suspect Widows
> probably orders the command is a subtly different order.
[...]

Or not the drive per se, but the USB-to-IDE/SATA chipset.

A while back on the OpenSolaris zfs-discuss list there was an issue where
USB drives would have corrupt ZFS pools if a drive was yanked without a
'zpool export' being run. Even though ZFS is supposed to always be
consistent on-disk (because it's transactional), this wasn't happening.

It turned that the chipset had a list of particular SATA commands that it
allowed through to the drive, and all others were simply answered with
"OK", regardless of what actual actions needed to be taken. One of the
SATA commands that was NOT whitelisted was the 'cache flush'
command--which ZFS needs to make sure that it's data structures were
written in the proper order.

Turns out the drive and its firmware were fine and doing things properly,
it's just that the necessary commands weren't getting to it because of the
USB adaptor's chipsset.