gmirror, gjournal and glabel - which order?

[Daniel Bye]

On Tue, Oct 13, 2009 at 01:08:46AM +0300, Manolis Kiagias wrote:
> Daniel Bye wrote:
> > Hi all,
> >
> > I'm having a hard time trying to work out which order I should set up
> > gmirror, glabel and gjournal on a new system. I want to journal my
> > /home partition, label all the partitions for ease of reference, and
> > use gmirror to save me in the event a disk goes bad. I am struggling
> > to fit the pieces together conceptually in my mind. I understand the
> > processes involved in setting each part separately - my problem is in
> > trying to build this up in the right order so that it all makes sense.
> >
> > So far, I have labelled the primary drive and set up the journal. I have
> > edited fstab to reflect the labels and journalled file system on /home.
> > If I now build a mirror, don't I need to alter fstab to mount that and
> > not the stuff in /dev/label? In which case, I guess I need to build the
> > mirror first, and then set up labels and journals?
> >
> > I'm going round and round in circles here and none of the stuff I've
> > read on the web enlightens me... :-/
> >
> > Any insights or suggestions would be taken as a great kindness!
> >
> > Dan
> >
> >   
> When not mirroring,  I first create the journals and then label the
> resulting adxxxx.journal devices
> In case you are doing a gmirror device, you would not really need the
> separate label step - the gm device name won't change and gmirror is not
> affected if the device names of the individual disks change (the disks
> are marked as part of a mirror and scanned at startup).
> When you are creating the composite gmirror device you are effectively
> labeling it anyway i.e. gmirror label gm0...
> Now if you follow the usual tutorials found in the web you would be
> using gm0 / gm1 but you actually name it any way you wish.
> If you really need to label the separate gmirrored partitions, do it
> after setting up the mirror.
> 
> Concerning the order of journals and mirroring, I  create the journals
> first, then mirror the result. This has always worked fine for me.

Thanks much, Manoli. After posting, I came to more or less the same
conclusion, but it's good to get confirmation from someone who clearly
knows more about this stuff than I do!

I'd still be interested to hear what others think/do.

As ever, thanks for your time.

Dan

-- 
Daniel Bye
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