Date: Thu, 5 Oct 1995 17:57:29 -0700 (MST) From: Terry Lambert <terry@lambert.org> To: bmk@dtr.com Cc: terry@lambert.org, serges@umr.edu, freebsd-questions@freefall.freebsd.org Subject: Re: tunefs Message-ID: <199510060057.RAA08389@phaeton.artisoft.com> In-Reply-To: <199510060005.RAA00822@everest> from "bmk@dtr.com" at Oct 5, 95 05:05:08 pm
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> > You could just update the in core copy without too much problem, since > > it's synced to disk on unmount. > > That's true - I had forgotten about that. Note the disclaimer. :) I have an unfair advantage. Try building a GUI-based interface for file system "properties" under Win95 and make it take effect immediately. 8-). > > I've been hacking logical volume management for partitions, extended > > partitions and BSD extended partitions (ie: the results of disklabel) > > for a port, and I'd like to get it all rolled together first. > > Hey, speaking of logical volume management, what are the chances of ever > seeing a software-based solution for striping, concatenating, and > mirroring of filesystems? It needn't be full-blown RAID, but it sure > would be nice to have some built-in fault tolerance. > Have you seen the disk suite for Solaris 2.4? Something along those > lines would be neat. The chances ought to be good; all it would take is work. 8-). When I'm talking about logical volume management, I'm talking about exporting "logical volumes" into the devfs disk device name space. Specifically, logical volume devisions (partitions) and logical-logical volume divisions (DOS extended file systems and the BSD diskalbel, which is almost exactly equivalent to a DOS logical extended partition). Basically this means exporting offset/range records into the devfs name space and causing accesses to apply those deltas and restrictions to the devices. Basically stackable sector translations. If you want to mount a DEC Alpha or PPC drive, you make sure you have a stacking layer that recognizes the logical volume management system in place on the drive. If you want to mount a floppy, you look there, as well (you won't find anything in the typical case, though PPC floppies have a partition table, at least the AIX ones do). Works for multiple sesions on a CDROM as well, and especially well with the new Microsoft CDROM Unicode file name format extensions to Orange Book. Volume concatentation would wok in the same paradigm, though I don't plan to implement it initially (unless I bite the bullet for JFS or NTFS; don't hold your breath for that, though). Striping is a special case of concatenation. Mirroring is a bit more involved. Media perfection should be handled at this level as well, for drives that don't support it intrinsically. Consider that if this is done, then there is not an issue of the bad sector replacements being at the end of the disk, inaccessable by the boot code. Nor is there an issue of the disklabel potentially living on a bad sector (making it unusable). That's all I was talking about. Terry Lambert terry@lambert.org --- Any opinions in this posting are my own and not those of my present or previous employers.
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