Re: shutdown sequence and UPS poweroff

[David Holland <dholland-tech%netbsd.org@localhost>]

On Fri, Jan 06, 2023 at 10:13:36AM -0500, Greg Troxel wrote:
 > Does it seem reasonably safe that mountall through root will be fast, < 10s?

We've been seeing scattered reports of unmounting taking fast amounts
of time, particularly on nvme devices, and I don't think we know why
yet.

It's a bug, but since not cutting the power to SSDs midflight is one
of the primary reasons to have a UPS these days... seems like a
dangerous on in this context. So it seems like a good idea to be
cautions.

Not sure what to recommend. The last time there was an issue like this
(which turned out to be a bad bug with cached data not being written
back until unmount time) it was possible to trigger the writing by
attempting an unmount you know will fail with EBUSY, but I don't think
we've ascertained if that works this go.

-- 
David A. Holland
dholland%netbsd.org@localhost