Date: Tue, 24 Jun 2003 13:03:25 +1000 From: Andrew Reilly <areilly@bigpond.net.au> To: Mohammad Nayyer Zubair <mzubair@ic.sunysb.edu> Cc: freebsd-fs@freebsd.org Subject: Re: ideas about a unioning file system Message-ID: <1056423804.48266.54.camel@gurney.reilly.home> In-Reply-To: <Pine.SOL.4.56.0306191803340.16978@sparky.ic.sunysb.edu> References: <Pine.SOL.4.56.0306191803340.16978@sparky.ic.sunysb.edu>
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Hi, On Fri, 2003-06-20 at 08:15, Mohammad Nayyer Zubair wrote: > Has anyone extensively used freebsd unionfs? From a system/network > administrator or from a kernel developer standpoint, what do you like > about it and what you dont like about it? I'm using unionfs thusly: # Device Mountpoint FStype Options Dump Pass# /dev/ad0s1a / ufs rw 0 1 /dev/vinum/mirror /home ufs rw 0 2 /dev/vinum/vinum0 /usr ufs rw,union 0 2 (sorry about the wrappage, cut and pasted from /etc/fstab.) There are other lines in /etc/fstab, of course, but these are the bulk of my workstation's file hierarchy. After years of tiny root partitions that eventually caused grief and breakage because of gradually expanding kernels/modules/cruft-in-etc, this time around I've made root about 500M and put the whole FreeBSD base system in there. So a buildworld/kernel/installworld touches everything in ad0s1a, and nothing else does (except /etc). This leaves the problem of what to do with /usr/ports, /usr/X11R6, /usr/local, /compat@->usr/compat, /tmp@->var/tmp, /var@->usr/var I could have mounted /dev/vinum/vinum0 somewhere like /usr1, and filled /usr with a bunch of symlinks, and I did that for a while. It's messy though, and quite a few things, like ports, bother to find their "true" path, so the /usr1 name leaks into config files and what-not. Ugly. Union mounting seems to be working for me. I do my backups, and it's not a super-heavily used system... Touch wood. > How should a unioning filesystem should behave? What specific features > would you like it to have? It should behave just the way it does: the stuff in /usr that was there before the mount stays there, and gets modified and all, just as it should be. Anything that wasn't in /usr before the mount gets written to the union partition. Reads see both. > Out of the previous efforts at a unioning file system like the Sun's TFS, > 3DFS, Plan 9 and FreeBSD unionfs itself, which fs do you think came close > to an ideal unioning file system? What's wrong with the one that we have? Cheers, -- Andrew Reilly <areilly@bigpond.net.au>
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