On Tue, Nov 10, 2009 at 4:29 AM, Nick Guenther <kou...@gmail.com> wrote: > So, as nicely summarized at > http://www.h-online.com/open/news/item/Possible-data-loss-in-Ext4-740467.html, > ext4 is kind of broken. It won't honor fsync and, as a /feature/, will > wait up to two minutes to write out data, leading to lots of files > emptied to the great bitbucket in the sky if the machine goes down in > that period. Why is this relevant to OpenBSD? Well sometimes I've been > writing a file in vi or mg and had my machine go down, and when it > comes back I find that the file is empty and I'm just trying to figure > out if this is just because the data wasn't fsync'd or if it's because > of softdep or what.
softdep has that effect. The file was created and then data written. But softdep cares more about the first op than the second, so there's a window where crashing will cause you to wake up with empty files. Without softdep, it's more likely you'll have your data (though it may even be the old version, and you may have to look in lost+found for it). softdep works fine with fsync, but the old unix trick of write data then rename leads to empty files, because the rename is "sped up" but the data isn't.
