[9fans] fossil 'halt' command?

[9fans] fossil 'halt' command?

[Venkatesh Srinivas]

Hi,

extract from the fossil paper:
> The block cache uses soft updates [1] to ensure that the on-disk file
> system is always self-consistent. Thus there is no halt console
> command and no need to check a file system that was shut down without
> halting.

Fossil does have a halt command and does often need checking after an
unexpected shutdown... Any reason why? Was it just observed that it was
needed? Or that soft updates weren't enough?

Thanks,
-- vs

Re: [9fans] fossil 'halt' command?

[Charles Forsyth]

i'd have thought that soft updates ensure consistency,
but a halt command ensures that all the changes are actually written.

Re: [9fans] fossil 'halt' command?

[erik quanstrom]

On Mon Apr 13 18:55:24 EDT 2009, forsyth@terzarima.net wrote:
> i'd have thought that soft updates ensure consistency,
> but a halt command ensures that all the changes are actually written.

i think your point is a good one and definately true
(and begs the question of disk caches), but given the paper,
one does wonder.  halt didn't show up until here
	http://9fans.net/archive/2003/04/218
but there are later notes, e.g.,
	http://9fans.net/archive/2003/11/66
that fossil was a bit difficult to shutdown cleanly.
i'm not sure if that was in reference to the chicken-and-egg
nature of the fossil/venti shutdown process or a problem
with fossil.

- erik