disklabel differences FreeBSD, DragonFly
xfb52 at dial.pipex.com
Thu Jul 27 19:15:15 UTC 2006
Mike Meyer wrote:
>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.
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.
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