RAID1 with gmirror
4711 at chello.at
Sun Oct 10 15:26:07 PDT 2004
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On Sunday 10 October 2004 18:58, Chris Elsworth wrote:
> On Sun, Oct 10, 2004 at 03:22:28PM +0200, Christian Hiris wrote:
> > # gmirror configure -v -b load mirror0 ad0
Yes, that should read "label" - sorry!
> I'm quite interested that you didn't bother re-labelling the new
> mirror device? I always thought that you had to (and I have been doing
No, re-labeling wasn't necessary. gmirror could read the existing labels and
created the corresponding mirror*s** devices showed up under /dev/mirror/.
fsck also went fine. I think this should work, as gmirror stores it's
metadata in the last sector of it's providers.
> 4) bsdlabel -e ad0 [taking into account the new 16 byte offset]
I never read about the new offset - until now I had no time to study the
gmirror code. Where did you find this interresting information?
> Is this all completely unnecessary? The first few times I played with
> gmirror, I was doing something similar to your method, but if you do
> bsdlabel -r /dev/mirror/mirror0s1 (or whatever) on your setup, don't
> you get warnings about partition sizes?
Yes, I get those warnings, too - but I decided to leave the labels as is,
because on a test array I found this working w/o any datacorruption.
An example in 'man gmirror' describes how to set up a gmirror array on a disk
with valid data. It uses 'gmirror lable' w/o extra labeling. I understand it
the way that the term 'valid data' means 'existing (non-gmirror-)data on an
already (before-gmirror-)labeled disk'. Maybe my understanding is wrong and
you gave me the hint to the reason why my mirrors break on startup. I will do
some testing on this.
The 2nd reason why I didn't touch my old labels, is that I want to be able to
step back to ataraid as simple as possible, just in case of a breakage of the
> That's what worried me enough
> to go through all the rigmarole above, which fixes those warnings.
I use gmirror since the day before yesterday, so for now there are still some
things that I couldn't test and possibly I overlooked some things. At a first
look, my experiences were not so bad, I lost no data and gained a lot of
flexibility in my hdd subsystem.
Christian Hiris <4711 at chello.at> | OpenPGP KeyID 0x3BCA53BE
OpenPGP-Key at hkp://wwwkeys.eu.pgp.net and http://pgp.mit.edu
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