Is update(8) a hack? (was: Re: 6386 shutdown: I CAN'T BELIEVE at&t was really this stupid!)
Marshall Cline
cline at suntan.ece.clarkson.edu
Fri Jun 23 03:52:08 AEST 1989
In article <2294 at drilex.UUCP> dricejb at drilex.UUCP (Craig Jackson drilex1) writes:
>Personally, I've always thought that update(8) was a hack, ever since I
>first saw it in Version 7. To think that someone would write an operating
>system that couldn't even keep its on-disk data structures consistent...
Sorry, don't agree. One of the philosophical issues upon which Un*x
is built is the separation of policy and mechanism. The kernel takes
care of mechanism, with as little policy as possible. (No one would
claim Un*x does a perfect at this separation, but it tries).
As applications get closer to the user, many policy decisions are made
(ex: the _kernel_ treats only two chars ['/' and '\0'] as special in a
filename, but the shell has lots of meta-chars; furthermore the
"-flag" system isn't special to the shell, but many applications
follow the getopt(3) route; etc).
Avoiding delayed-write would, in general, bring performance down
pretty badly. Given an OS that _does_ have delayed-write, the only
question is: how often should we "sync" the system? Personally, I
think this _policy_ decision should be left _OUT_ of the kernel.
Marshall
--
________________________________________________________________
Marshall P. Cline ARPA: cline at sun.soe.clarkson.edu
ECE Department UseNet: uunet!sun.soe.clarkson.edu!cline
Clarkson University BitNet: BH0W at CLUTX
Potsdam, NY 13676 AT&T: 315-268-6591
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