Date: Fri, 04 Jan 2008 01:56:19 -0800 From: "Chris H." <chris#@1command.com> To: Clifton Royston <cliftonr@lava.net> Cc: freebsd-stable@freebsd.org Subject: Re: gmirror on 7B4 Message-ID: <20080104015619.w1qyx0b7wo8cc00g@webmail.1command.com> In-Reply-To: <20080103192526.GA18773@lava.net> References: <20080102002651.r72jwx0pgk4000c8@webmail.1command.com> <20080102070518.ki0v7vxkgo0cossg@webmail.1command.com> <20080102111751.5huybrwosgs0ccos@newwebmail.jnielsen.net> <20080102112230.g7p1bj3sdck488g8@newwebmail.jnielsen.net> <20080102084743.xtecj951wogwws8w@webmail.1command.com> <20080103192526.GA18773@lava.net>
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Quoting Clifton Royston <cliftonr@lava.net>: > On Wed, Jan 02, 2008 at 08:47:43AM -0800, Chris H. wrote: >> Quoting John Nielsen <lists@jnielsen.net>: >> >> >I'm not sure I remember everything from earlier in this thread so I >> >don't know if it's relevant, BUT you can't boot from a gstripe volume >> >(or from a gconcat one AFAIK). Inferring from your fstab example >> >below it doesn't sound like you intend to but I just wanted to be >> >sure. >> >> Are you sure? I read that using gmirror requires /kernel to be located >> in the /boot slice and everything else (all other slices) can be mirrored >> safely. But in all my reading (man pages, FBSD handbook, asstd articles) >> I haven't seen anything indicating booting wasn't possible from a gstripe >> volume. > > Your current idea is backwards; you can boot from entirely mirrored > drives (i.e. RAID1) and I've been doing it since 5.3, but AFAIK it is > impossible to boot from a striped drive and I suspect will remain so > for a long time. > > One way to visualize this is to recognize that because the gmirror > information is stored at the very end of the lower-level GEOM object, > each of the raw drives in the mirrored set appears to be an perfectly > normal drive when reading it from its beginning; thus it is possible to > simply read it as a normal device during the earlier stages of boot > until GEOM and gmirror loads. With striping, however, the logical > content is spread out across multiple drives, so any one drive you try > to boot from has only 1/Nth of the relevant sectors. Indeed, and thank you for pointing out the obvious to me. :) I was almost immediately reminded of that after posting. :P But really, I appreciate your taking the time to /enlighten/ me. It /does/ help. Given the /wealth/ of information afforded to me here on the list, after proposing my intentions. It quickly occurred to me that I had developed quite a few misconceptions about GEOM and friends, and that I should have taken just a bit more time before leaping. In the final analysis, I think it would be /far/ more efficient if I simply blanked my current disk, and simply laid it out as I ultimately want it. Then simply unarc the root folders to their desired destinations from the most recent backups. Which kind of makes this thread a loop. As my initial question was why wasn't gMIRROR part of sysinstall. It's funny, I've spent over 2 decades running *BSD, and yet I never really spent much time obtaining intimate knowledge about the disk "construction". Oh, it's not that I know nothing about it. But rather, that once I determined the ultimate layout for my needs, I simply let sysinstall handle it. So other than needing to add disks and move/ re-create slices, I was done. But as I now revisit it, I discover I should probably spend a little more time acquainting myself with it. :) Thanks again for taking the time to respond. I appreciate it. Chris > > Does this help? > > -- Clifton > > > -- > Clifton Royston -- cliftonr@iandicomputing.com / cliftonr@lava.net > President - I and I Computing * http://www.iandicomputing.com/ > Custom programming, network design, systems and network consulting services > _______________________________________________ > freebsd-stable@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-stable > To unsubscribe, send any mail to "freebsd-stable-unsubscribe@freebsd.org" > -- panic: kernel trap (ignored)
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