Subject: running *without* softdep unsafe?
To: None <firstname.lastname@example.org>
From: Todd Vierling <email@example.com>
Date: 05/25/2000 11:41:21
I understand that softdep is great and peachy, et al., but something just
struck me as strange.
We are no longer building update(8) as part of the distribution. Doesn't
this assume that the admin _is_ using the [GPL'd] softdep? After all,
update(8)'s purpose is to call sync() every 30 seconds or so to keep the
data blocks and metadata as up-to-date as possible.
Extreme case: Let's say I have a non-softdep system, under very light load,
and issue a write() to a file. It's buffered, of course, so the buffer
cache (page cache? Are we doing UBC in the trunk yet?) is holding on to the
data. _Nothing_ in userland happens for another 30 minutes--in particular,
sync() or write() are not called again--and the system loses power. Would
that write() ever have made it to disk for sure?
-- Todd Vierling (firstname.lastname@example.org)