volume management

[Rick C. Petty]

On Tue, Apr 10, 2007 at 01:41:15PM +0200, Pawel Jakub Dawidek wrote:
> On Tue, Apr 10, 2007 at 01:32:02PM +0200, Ivan Voras wrote:
> > Pawel Jakub Dawidek wrote:
> > 
> > >1. Panic if there is no physical storage. This way you protect
> > >   consistency. You already printed a warning that gvirstor is running
> > >   out of physical storage, so administrator has a chance to do the job.
> > 
> > I really don't want to do that :(
> 
> If you have important data, this is really not bad idea. I, for one,
> prefer my kernel to panic, so I can see what exactly went wrong, add
> another disk and reboot instead of allowing kernel goes into wild by
> returning an error which won't be handled properly.

It's a terrible idea!  What happens to all uncommitted soft updates and
other unwritten cached blocks?  Lost forever, which can have bad effects on
file systems and at the very least require everything to be fsck'd and GEOM
mirrored or raid objects to be resync'd.  What's wrong with ENOSPC?  Isn't
that the whole point of that error?  Let the admin know that something
failed, don't panic and prevent any further operation period.

I know I don't want my fileserver to panic just because I accidently try to
add 100 GB instead of 10 GB or some other simple miscalculation.  We have
enough panics in the kernel already for cases that should be handled better
in userland.

-- Rick C. Petty