Date: Tue, 21 Feb 2006 13:50:27 +0200 From: Ruslan Ermilov <ru@freebsd.org> To: Eivind Olsen <eivind@aminor.no> Cc: freebsd-stable@freebsd.org Subject: Re: gmirror is confusing me, will I be bitten by the last-sector-use? Message-ID: <20060221115027.GB60211@ip.net.ua> In-Reply-To: <43FAE446.4090807@aminor.no> References: <43FAE446.4090807@aminor.no>
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[-- Attachment #1 --] On Tue, Feb 21, 2006 at 10:58:30AM +0100, Eivind Olsen wrote: > Hello. > > I've just configured a server to use gmirror (using FreeBSD 6.1b2). I > followed the tutorial on > http://www.onlamp.com/pub/a/bsd/2005/11/10/FreeBSD_Basics.html and did > it install-time. > Then I read in the gmirror(8) man-page that gmirror uses the last sector > of the provider to store metadata. > > My mirror consists of two IDE-disks/consumers (ad0 and ad3), both > showing a mediasize of "250059350016 (233G)" in "gmirror list". The > provider is shown as having a mediasize of 250059349504. Sectorsize = 512. > > Now, how can I check whether my current partitions will cause trouble > with the metadata-sector or not? I've done some searching on the net, > but I'm still a bit confused. If I understand correctly, the consumers > ad0/ad2 span 488397168 sectors (mediasize/sectorsize), and the > mirror/gm0 spans 488397167 sectors. > In short: kernel (g_mirror) won't let you write to the last sector of its media. > Here's the output from bsdlabel: > > vimes# bsdlabel /dev/mirror/gm0s1 > # /dev/mirror/gm0s1: > 8 partitions: > # size offset fstype [fsize bsize bps/cpg] > a: 6291456 0 4.2BSD 2048 16384 28552 > b: 4194304 6291456 swap > c: 488392002 0 unused 0 0 # "raw" part, > don't edit > d: 41943040 10485760 4.2BSD 2048 16384 28552 > e: 2097152 52428800 4.2BSD 2048 16384 28552 > f: 31457280 54525952 4.2BSD 2048 16384 28552 > g: 31457280 85983232 4.2BSD 2048 16384 28552 > h: 370951490 117440512 4.2BSD 2048 16384 28552 > > So, the "h" partition, which is the last one, has offset=117440512 and > size=370951490, and if I add those together I get 488392002. Does this > mean that my "h" partition ends at 488392001 (right before 488392002), > and I'm still several sectors away from the metadata? Or am I > misunderstanding things here? > Your "c" partition (the whole disk) occupies 488392002 sectors. The "h"'s partition last sector is 117440512+370951490-1=488392001. Cheers, -- Ruslan Ermilov ru@FreeBSD.org FreeBSD committer [-- Attachment #2 --] -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.2 (FreeBSD) iD8DBQFD+v6DqRfpzJluFF4RAnLeAJ9ustWschedFxAwMWChBcHdgsTX0gCfYCf9 mekJbfHSL3mdjA92i/poFd4= =XbYc -----END PGP SIGNATURE-----help
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