Date: Thu, 27 Jul 2006 20:15:10 +0100 From: Alex Zbyslaw <xfb52@dial.pipex.com> To: freebsd-hackers@freebsd.org Subject: Re: disklabel differences FreeBSD, DragonFly Message-ID: <44C910BE.9000108@dial.pipex.com> In-Reply-To: <17609.1474.618423.970137@bhuda.mired.org> References: <20060727063936.GA1246@titan.klemm.apsfilter.org> <20060727122159.GB4217@britannica.bec.de> <20060727134948.GA3755@energistic.com> <20060727180412.GB48057@megan.kiwi-computer.com> <17609.1474.618423.970137@bhuda.mired.org>
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Mike Meyer wrote: >In <20060727180412.GB48057@megan.kiwi-computer.com>, Rick C. Petty <rick-freebsd@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. --Alex
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