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

[Ram Ramesh]

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?

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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[NeilBrown]

Post by Ram Ramesh
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

Post by Ram Ramesh
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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[Ram Ramesh]

Good to know. Thanks.

Ramesh

Post by NeilBrown

Post by Ram Ramesh
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

Post by Ram Ramesh
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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