From mboxrd@z Thu Jan  1 00:00:00 1970
From: starlight.2012q4@binnacle.cx
Subject: Re: question: no-bitmap RAID1 with off-site drive
Date: Mon, 12 Nov 2012 12:26:25 -0500
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After some pondering, think I've figure it out.

Best way to go is to set it up with

  --create --level=1 --raid-devices=2

for the initial pair of drives, then

  --fail --remove

the rotate-out drive, then

  --add

the alternate drive.  Now there will be
three drive slots with one "removed" and two
"active".

To rotate a drive off-site

   --fail --remove

go to the off-site, swap the drives and on return

   --re-add

the rotate-in drive.

This way the 'mdadm' UUID labels will stay on the
drives and 'mdadm' will warn against mistakes
such as trying to use the wrong drive for
a mirror pair.  Will always have one "removed"
drive.

The

   --grow --raid-devices=1 --force

and

   --grow --raid-devices=2 --add

would be used only if a drive fails and needs to
be replaced.

If anyone disagrees please advise.