Date: Tue, 03 May 2005 21:26:43 +0200 From: Eirik =?ISO-8859-1?B?2A==?=verby <ltning@anduin.net> To: <hartzell@alerce.com> Cc: "stable@freebsd.org" <stable@freebsd.org> Subject: Re: gmirror oddities Message-ID: <BE9D9D13.1488C%ltning@anduin.net> In-Reply-To: <17015.50206.651588.618737@satchel.alerce.com>
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On 03-05-05 20:34, "George Hartzell" <hartzell@kestrel.alerce.com> wrote: > > Eirik Øverby writes: >> Hi! >> >> I've been using gmirror for a while to safeguard my system disks. I have >> taken the slice-based mirror approach, where I use, say, ad0s1 and ad2s1 as >> providers. >> On one of my servers, this seems to be impossible. I create the mirror using >> ad2s1 first (to keep my system running while I do some of the work), and >> then I re-initialize ad0s1 (making it exactly the size of ad2s1) before >> using gmirror insert to add it to the mirror. >> However, at this point - when doing a gmirror list - it turns out that it >> never added ad0s1 as a provider, but ad0 itself! As a result, I now have a >> load of slices (ad0a, ad0b, ad0d, ad0e, ad0f) instead of having the same >> structure as I have on ad2s1. It's just like ad2s1, just without the "s1" >> part. >> >> I've tried "dd if=/dev/zero of=/dev/ad0 bs=65536" a couple of times, in case >> some old provider metadata was stored there. I also have exactly the same >> setup in another server, the only difference being that it behaves as >> expected.. >> >> Am I doing something blatantly wrong here? This IS supposed to work, right? >> I've even found a very nice description of how to do it at >> http://people.freebsd.org/~rse/mirror/ >> confirming that what I'm doing is right. >> >> I'm on 5.4-PRERELEASE, but this problem has been there since 5.3-p2 or >> something, which was when I first tried this. > > I bet you're getting bitten by a problem that bit me. It's described > in the fine print in http://people.freebsd.org/~rse/mirror/. > > Gmirror saves it's metadata on the last sector of its disk space. > Since the slice (adXs1) and the disk device (adX) end at the same > place on the disk, gmirror gets confused. It tastes devices in a > particular order, apparently devices first, then slices. It finds the > metadata when it tastes adX and goes ahead and uses it, even though it > should be associating it w/ adXsY. Hilarity ensues.... > > The fix is described in the fourth comment block of Ralf's doc, either > make the slice a sector smaller than the disk device or hardcode the > provider name. I've been using the hardcoding approach, and it seems > to work for me. Same here, tried that immediately after my last post. Apologies for the noise ;) /Eirik
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