Date: Sat, 20 May 2006 15:03:06 +0200 From: Pawel Jakub Dawidek <pjd@FreeBSD.org> To: "Rick C. Petty" <rick-freebsd@kiwi-computer.com> Cc: James Snow <snow@teardrop.org>, freebsd-geom@freebsd.org Subject: Re: Slices + stripes and mirrors Message-ID: <20060520130306.GA7030@garage.freebsd.pl> In-Reply-To: <20060519180604.GA37562@megan.kiwi-computer.com> References: <200605161555.08195.darcy@wavefire.com> <20060517171955.GB838@garage.freebsd.pl> <20060519172148.GA54819@teardrop.org> <20060519180604.GA37562@megan.kiwi-computer.com>
next in thread | previous in thread | raw e-mail | index | archive | help
[-- Attachment #1 --] On Fri, May 19, 2006 at 01:06:04PM -0500, Rick C. Petty wrote: +> On Fri, May 19, 2006 at 01:21:49PM -0400, James Snow wrote: +> > On Wed, May 17, 2006 at 07:19:55PM +0200, Pawel Jakub Dawidek wrote: +> > > On Tue, May 16, 2006 at 03:55:07PM -0700, Darcy Buskermolen wrote: +> > > +> +> > > +> I have a 6.1 setup with 4 identical 300GB disks, ad4,6,8,10. I'd like to +> > > +> create a bootable mirror (gm0s1) of all 4 disks on a 512MB slice, and have +> > > +> the remaining space a big slice (gs0s2). +> > +> > I'm going something almost identical and have been having some +> > difficulty. +> +> Who don't people use gvinum more? These more complex setups require more +> flexibility. Also gvinum will let you grab the full disks and not deal +> with mirroring the slices individually. Using gmirror on slices seems +> pretty hackish to me. Maybe for you. This what GEOM infrastucture gives you - you don't care if this is a disk, slice, partition, mirror device, encrypted device, etc. It is provider and you can do whatever you need to do with it. This is the flexibility. Imagine a configuration where you have 5 disks. Create one 2GB slice on all disks, and use the rest space for the second slice. Now, create root file system by mirroring da0s1a and da1s1a. Create /usr/ on raid3(da2s1, da3s1, da4s1) and create /home/ on raid3(da0s2, da1s2, da2s2, da3s2, da4s2). This is the flexibility. +> > > Ok, first initialize your disks and create two slices on them: +> > > +> > > # apply "fdisk -Bi /dev/ad%1" 4 6 8 10 +> > > +> > > (If they are identical, you can probably initizlize one of them and copy +> > > first 63 sectors to the others.) +> > > +> > > Once you have your slices, create a mirror: +> > +> > I've been using Ralf's guide[1] for the basics of this, and he mentions +> > that you need to shrink the slice by one sector. Is this still the case +> > in 6.1? If so, when doing two slices per disk, do you need to shrink +> > both slices by one sector, or only the last slice on the disk? +> +> The reason you nede to shrink the slice is because the metadata for gmirror +> is stored on the last sector of the provider (which in this case is a +> slice, but usually is just the disk). Because the metadata is stored for +> each instance in the mirror, every slice you mirror will shrink by one +> sector. Because you are mirroring slices not disks, gmirror doesn't "know" +> about the disks. Again, this method seems very hackish. If you mirror the +> entire disk, gmirror will provide a device that is one sector smaller than +> the disk.. this should be transparent. If you're not mirroring the entire +> disk, I think you're halfway down a dangerous path. Hehe, cool. So check by yourself how gvinum is transparent:) It doesn't use metadata?:) I'm sure it takes much more than one sector. And again. You simply don't understand what for GEOM was actually introduced... +> In any case, I've had better luck using gvinum even for just plain +> mirroring. Also, I feel that his guide implies setting up mirroring is +> less than trivial. IMO, it's easier to use a livecd since you have to +> reboot the box anyway. For that number of steps, why not use gvinum +> instead? You'd have more flexibility and you can do things like resize +> volumes and add/remove drives while the system is up. You can't add/remove gmirror's component which the system is up? Resizing should be done with another GEOM class. -- Pawel Jakub Dawidek http://www.wheel.pl pjd@FreeBSD.org http://www.FreeBSD.org FreeBSD committer Am I Evil? Yes, I Am! [-- Attachment #2 --] -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.2 (FreeBSD) iD8DBQFEbxOKForvXbEpPzQRAowDAJ9me2Su4Xc46z8TZdB8IZfYjotsgQCaAgX7 +z2IsSnFTkD5aeBTdf0AH+c= =zEzj -----END PGP SIGNATURE-----
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20060520130306.GA7030>