Re: mdadm --grow with --backup-file does not create backupfile?

[NeilBrown <neilb@suse.de>]

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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
> 
>     sudo mdadm --grow --raid-devices=5
>     --backup-file=/root/grow_md0.bkp_file --layout=normalise /dev/md0
> 
> I got a response that stated that mdadm needed to backup 384K of data. 
> However, when I checked after about 5min there was no backup file. Is 
> 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 the
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



> 
>     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
> 
> Ramesh
> 
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