disklabel differences FreeBSD, DragonFly

Mike Meyer mwm-keyword-freebsdhackers2.e313df at mired.org
Thu Jul 27 18:28:42 UTC 2006

In <20060727180412.GB48057 at megan.kiwi-computer.com>, Rick C. Petty <rick-freebsd at kiwi-computer.com> typed:
> On Thu, Jul 27, 2006 at 09:49:48AM -0400, Steve Ames wrote:
> > On Thu, Jul 27, 2006 at 02:21:59PM +0200, Joerg Sonnenberger wrote:
> > > DragonFly disklabels allow 16 entries by default, FreeBSD still limits
> > > it to 8. That's why you can't read it directly.
> > Are there plans to bump the default up from 8? I'm honestly torn on
> > this topic whenever I install a new system. On the one hand I like
> > having a lot of discrete mountpoints to control potential usage. On
> > the other hand with drive space being so inexpensive I sometimes
> > wonder if I need to bother and can get away with very few mountpoints.
> I would think that cheap disk space would mean larger disks which implies
> more mountpoints ???

Nope. One of the historical uses of partitions was to act as firewalls
between subsystems, so that subsystem A running out of space didn't
cause subsystem B to die for lack of space. This had the downside of
making it more likely that one of the two would run out of space
because the excess space from another subsystem could only be used by
it. With cheap disk space, you overallocate by enough to give you
plenty of warning before you have to deal with the issue. You can
safely share that space, and doing so means you have to "deal with the
issue" less often.

These days, the only technical reason I know of for having separate
mountpoints is because you want to run commands that work on
filesystems on the two parts with different arguments or under
different conditions.

> I wasn't very happy with gpt or bsdlabel recently because you aren't
> allowed to modify the partitions if the gpt/bsdlabel is in use (i.e. one
> of the other partitions is currently mounted as a filesystem).  I hope the
> GEOM people are working to improve this.

Yet another reason for having fewer partitions: you're less likely to
want to modify them :-).

Mike Meyer <mwm at mired.org>		http://www.mired.org/consulting.html
Independent Network/Unix/Perforce consultant, email for more information.

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