Prevent USB3 hard drive from spinning down

[Benny Siegert <bsiegert%gmail.com@localhost>]

Hi folks!

I have an external hard drive with USB 3 connection, based on a
Promise USB-SATA bridge. (This is on NetBSD-current, amd64.)

Unfortunately, after a few minutes of inactivity, the controller will
spin down the hard drive. Any access after that (even unmounting the
file system there) leads to the process hanging forever. There are
kernel messages mentioning IOERROR and TIMEOUT. Even rebooting will
hang.

- Is there a way to prevent the drive from spinning down? Perhaps some
atactl command?
- Once the drive has spun down, how do I get out of this state
cleanly? Turning the disk off and on again does not work.

--Benny.