From mboxrd@z Thu Jan  1 00:00:00 1970
From: NeilBrown <neilb@suse.de>
Subject: Re: mdadm --grow with --backup-file does not create backupfile?
Date: Mon, 13 Oct 2014 12:39:14 +1100
Message-ID: <20141013123914.04b960ed@notabene.brown>
References: <543B2A2D.9080407@gmail.com>
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To: Ram Ramesh <rramesh2400@gmail.com>
Cc: Linux Raid <linux-raid@vger.kernel.org>
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On Sun, 12 Oct 2014 20:26:05 -0500 Ram Ramesh <rramesh2400@gmail.com> wrote:

> I added a new disk and grew my raid6 md0 with the following command line
>=20
>     sudo mdadm --grow --raid-devices=3D5
>     --backup-file=3D/root/grow_md0.bkp_file --layout=3Dnormalise /dev/md0
>=20
> I got a response that stated that mdadm needed to backup 384K of data.=20
> However, when I checked after about 5min there was no backup file. Is=20
> this expected?

Yes.

When increasing the size of an array, the backup file is needed  for a tiny
fraction of a second at the start.
When decreasing the size it is needed  for a tiny fraction if a second at t=
he
end.
When the size isn't changed it is needed for the entire time.

... unless you have a new kernel and a new mdadm, and then the backup file
isn't needed.

NeilBrown



>=20
>     386 > sudo ls /root
>     <no files. so no output>
>     387 > sudo ls /root/grow_md0.bkp_file
>     ls: cannot access /root/grow_md0.bkp_file: No such file or directory
>=20
> Ramesh
>=20
> --
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