Many file servers using disk drives are "unreliable" if you shut them down
without saving data in memory first.
Both /sys/src/fs and disk/kfs force certain metadata updates to disk first
to try to ensure that the fs structure,
if not the content, remains consistent. In fact, disk/kfs does more than
the old file server (it forces indirect block
updates out as well). Disk/kfs only seemed less reliable than the old file
system because it is more likely
to be shut down without syncing. Also, the old file server could be
recovered from a consistent root
if the worm dump was used. If you sync, you shouldn't have too much trouble.
Of course, forcing write-through makes the file system slower than some
others
for updates. At the cost of some code complexity, fossil attempts to do
better, using a "soft update"
scheme to ensure or attempt to ensure that everything on disk is
consistent. It's mentioned
briefly in the paper.

On 25 December 2011 16:30, Aram Hăvărneanu <aram.h@mgk.ro> wrote:

>  I
> have heard very good things about the reliability of both.  You say
> kfs is not very reliable, oh well.
>