Re: GEOM: gpt partitions on a gmirror array possible?

On Sat, Nov 27, 2004 at 07:58:35PM +0000, Chris Hedley wrote:
+> Hi all,
+> 
+> A hopefully quick question!  I have looked for a solution for (or 
+> discussion about) this, if I've just failed to find it, please point me in 
+> the right direction.
+> 
+> This is what I'm trying to do: I've created a RAID-1 array, m1, using 
+> gmirror on two scsi units, da0 and da1, and I'd like to chop it up into 
+> logical partitions using gpt, as I understand (correctly, hopefully) there 
+> are leanings toward gpt rather than bsdlabel as being the correct way to 
+> do things.  Now when I initialise and create my gpt partition on 
+> mirror/m1, I get no new entries in /dev/mirror but I _do_ get separate 
+> /dev/da0p1 and /dev/da1p1 entries appearing.  I've probably completely 
+> failed to understand the whole concept of GEOM tasting and unprejudiced 
+> hierarchy and so on as I decided I may as well try to create my UFS2 
+> filesystem on /dev/da0p1 in /dev/mirror/m1p1's absence and see if 
+> /dev/da1p1 magically follows suit.  Needless to say it doesn't, I just end 
+> up with a dirty RAID-1 disc that needs resynchronising, with da0p1 
+> (un)mysteriously disappearing after the newfs.
+> 
+> Is there a correct way to do this, or am I once again guilty of trying to 
+> use something that isn't quite ready yet?  Perhaps I should do it the 
+> other way around and use gpt first and create one gmirror per partition; 
+> that solution didn't "feel" right for some reason, but I can't really 
+> quantify that particularly as, if I understand the GEOM documentation 
+> correctly, multiple gmirrors with their respective paritions on the same 
+> set of discs shouldn't compete with each for access.
+> 
+> My system is FreeBSD/amd64, 6.0-current (Oct 25th vintage) using ahc for 
+> my test scsi discs and aac for my active discs.

It is because GEOM_GPT class only allow to create GPT labels on rank#1
providers (i.e. disks). I'm not sure why we have this hack, maybe marcel_at_
knows something more (cc'ed).

-- 
Pawel Jakub Dawidek                       http://www.FreeBSD.org
pjd_at_FreeBSD.org                           http://garage.freebsd.pl
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