Unionfs and nullfs question

[Vulpes Velox]

On Sat, 23 Oct 2004 11:47:57 -0300 (ADT)
"Marc G. Fournier" <scrappy at hub.org> wrote:

> On Fri, 22 Oct 2004, Vulpes Velox wrote:
> 
> > I am guessing the answer, given the big warning in the man for
> > both is that this is going to be a no that both are dangerous to
> > the data and luck is mainly involved in not having the data
> > screwed over, but just wanna check :)
> 
> I run over 200 VPSs over 4 machines with all application data
> (installed ports) mounted through unionfs to reduce disk space usage
> ... every once in a blue moon, I'll get a crash resulting from a bug
> in the unionfs code, but it isn't as bad as it was, say, a year ago
> ... but I am running production servers with it.
> 
> There are a few things you can't do right now ... for instance, I
> don't have /var union mounted, as FIFO's/sockets tend to
> consistently blow it up ... but, my more loaded server looks like:
> 
> # df -t union | wc -l
>        73
> # uptime
> 11:41AM  up 47 days, 22:25, 1 user, load averages: 12.12, 20.67,
> 22.46
> 
> There is an annoying 'bug' in fsck that Don Lewis has been working
> on correcting that is very exasperated by unionfs ... namely how the
> list of inodes to check is generated.  If you, for instance, mount a
> blank file systems over top of /usr/ports, and then do a find of
> /usr/ports, the blank file system will fill up with a bunch of
> directories to 'mirror' ports ... the files don't come through, only
> the directories.  On a crash, the OS leaves behind a bunch of ZERO
> LENGTH DIRECTORIES ... I've had fsck run for 12-14hrs after one of
> these, its that messy :(  Don has been working on a patch to handle
> the ZLDs better, but it hasn't been committed to -stable yet,
> pending more testing ... I'm running it live here, but *knock on
> wood* haven't had a crash since putting it into place ...


Cool, thanks for the info.

I eventually decided to go with doing a mount_nfs -o union for it :)
>From one of the conversations I found previously, this is suppose to
be safer than doing doing a regular mount_unionfs.