Re: disklabel differences FreeBSD, DragonFly

Mike Meyer wrote:

In <20060727180412.GB48057@xxxxxxxxxxxxxxxxxxxxxxx>, Rick C. Petty <rick-freebsd@xxxxxxxxxxxxxxxxx> 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.


You assume that "running out of space" happens over time, but with some runaway process logging to a file, for example, the partition filling up will still happen without you expecting it. It might take a bit longer with a big disk, but 20 minutes instead of 5 minutes isn't much different in terms of warning. Fill /tmp or /var and many things can fail. Fill /home and it's just users who suffer a little but mail, demons etc. just carry on.

A further reason to separate partitions is that dump works at the level of a partition. Different partitions may have very different backup requirements, and for those of us without huge tape drives, partitioning to a size that can be dumped on one tape makes life easier.

In some environments, fewer partitions may indeed be the new norm, but in others it would not.

Personally, I would like a limit of 16. It would mean that I could fit all my regular partitions inside a single slice, freeing up other slices for, for example, experimenting with 64-bit, or -current, or whatever. Bootable FreeBSD slices will be stuck at 4 for the foreseeable future - extending the number of partitions within a slice frees up slices, which are the really limited resource.

I have no real idea how hard it would be to extend from 8 to 16, but if the effort required were reasonably low, then it would get my vote.

--Alex


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