Date: Fri, 26 Nov 2004 09:23:40 +0100 From: Pawel Jakub Dawidek <pjd@FreeBSD.org> To: Jo?o Carlos Mendes =?iso-8859-2?Q?Lu=EDs?= <jonny@jonny.eng.br> Cc: freebsd-hackers@freebsd.org Subject: Re: gmirror bugs, how many? Message-ID: <20041126082340.GC7232@darkness.comp.waw.pl> In-Reply-To: <41A6B76F.4020101@jonny.eng.br> References: <41A4FD60.4050501@jonny.eng.br> <20041125224547.GB7232@darkness.comp.waw.pl> <41A6B76F.4020101@jonny.eng.br>
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[-- Attachment #1 --] On Fri, Nov 26, 2004 at 02:56:15AM -0200, Jo?o Carlos Mendes Luís wrote: +> Pawel Jakub Dawidek wrote: +> >First mistake - wrong order. Create a mirror, than partition a mirror +> >provider. +> +> Is this a constraint in the design? Im my point of view, geom would +> treat all block devices equally, no matter if they are whole disks or +> single partitions. You're right and it does so. +> If this is not the case, them maybe this should be noted in the man page. +> +> Note that sometimes it is not necessary to have a whole disk redundant. +> I could use part of it to temporary data, for example. I've done this +> with vinum in 4-stable more than once: I get two disks, each with a copy +> of the root partition (which I intended to mirror with gmirror), a swap +> partition, a mirror vinum subdisk and a stripe vinum subdisk. Note that +> in this case the data integrity and cost is more important than +> continuous operation. If a disk fail, the server will stop, but no +> *important* data will get lost. This is the scenario which I was testing. You can do that with gmirror. All I'm saying is that you first should create a mirror, then create slices and partitions on top of mirror provider, because you want to use mirror/vol0s1a, not ad0s1a. Note, that mirror/vol0 is one sector shorter than ad0 and imagine a situation when gmirror stores metadata in the same place where BSD stores it - if you first create a mirror and then partitions on ad0 you'll overwrite gmirror metadata. This very painful, that in MBR metadata is visible on traffic providers and I don't want to repeat that mistake. +> >+> Now, lets reboot. I could not unload geom_mirror, since it was +> >+> preloaded during boot, is this expected? The device could not be +> >+> unloaded, but the volume disapeared (gmirror list, ls /dev/mirror). +> > +> >If there is no mirror configured, you should be able to unload it. +> +> Before putting it in /boot/loader.conf, unload worked, even with mirror +> devices configured, IIRC. Only after loader.conf preloading this +> problem appeared. What error do you get when you try to do this? +> The man page says only: +> +> -h Hardcode providers' names in metadata. +> +> and does not explain when I should use this. +> +> Do you mean that if I want it to use ad1s1 as the provider, and not ad1, +> -h is what I want? Only when you share the last sector between those two providers. You can still create ad1s1, which is one sector shorter. +> > +> >+> Is there any gmirror hacker around to fix these? +> > +> >There is nothing to fix. +> +> Surely there is. At least the manual. I've to agree here.:) +> And even if gmirror is correct, there's also the problem shown with +> disklabel in my previous email. What problem is there when you use proper order of doing things? -- Pawel Jakub Dawidek http://www.FreeBSD.org pjd@FreeBSD.org http://garage.freebsd.pl FreeBSD committer Am I Evil? Yes, I Am! [-- Attachment #2 --] -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.4 (FreeBSD) iD8DBQFBpugMForvXbEpPzQRAlaZAJ94XHe06WhbEQIG0hEg89I++GBEIwCeKGmR DzedhLHUa7o6bDKfSjqx/tw= =fby2 -----END PGP SIGNATURE-----
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