Re: [linux-lvm] Is MD array (containing a PV) reducible?

From: "Brian J. Murrell" <brian@interlinx.bc.ca>
To: linux-lvm@redhat.com
Subject: Re: [linux-lvm] Is MD array (containing a PV) reducible?
Date: Wed, 04 Oct 2023 13:59:34 -0400	[thread overview]
Message-ID: <588df601b080ad0f69b36e86fd1d7bcd6380af6e.camel@interlinx.bc.ca> (raw)
In-Reply-To: <87wmw2le5j.fsf@vps.thesusis.net>

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On Wed, 2023-10-04 at 09:18 -0400, Phillip Susi wrote:
> 
> Yep.

Much thanks.

But I did just think of the other benefit of using MD to sync the new
device and that's having a recovery path.

That is, if I add luks-backup to /dev/md0 and then wait for it to
finish syncing, I can then shut down the machine, remove /dev/sdc from
the machine and start it back up and ensure that all of the needed
initialization bits are in place to make the luks component come up and
be readable.  If it is, I just remove it from md0 and use it stand-
alone (as it is itself a RAID-1 recall).  Reboot again to make sure
it's all still working and good.

If any of the above goes sideways, I still have the sdc disk as an md0
member and can put it back in the machine to get back to my starting
position and try again, trying to figure out where I went wrong.

With pvmove, once the move is complete there is no going back to my
starting position if something is not right and I cannot access my new
luks device.

So given that, and given that I have stared my pvmove with --atomic and
--interval, do I just SIGINT the pvmove?  Or should I do pvmove --abort
on another terminal?  How can I know when the the abort is complete and
that I can vgreduce luks-backup out of the backups volume group?

Once I have vgreduced, is there anything I should do to
/dev/mapper/luks-backup before I mdadm --manage /dev/md0 --add
/dev/mapper/luks-backup just to wipe any remnants of it being a PV
previously?

I really do appreciate all of the help, advise and patience you have
given/shown me.

Cheers,
b.

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