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

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

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

[NeilBrown]

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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
> 
> --
> To unsubscribe from this list: send the line "unsubscribe linux-raid" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html


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

[Ram Ramesh]

Good to know. Thanks.

Ramesh

On 10/12/2014 08:39 PM, NeilBrown wrote:
> 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
>>
>> --
>> To unsubscribe from this list: send the line "unsubscribe linux-raid" in
>> the body of a message to majordomo@vger.kernel.org
>> More majordomo info at  http://vger.kernel.org/majordomo-info.html