[CentOS] more software raid questions

[Rob Kampen]

Rudi Ahlers wrote:
> On Wed, Oct 20, 2010 at 4:34 AM, Nataraj <incoming-centos at rjl.com> wrote:
>   
>> When I create my Raid arrays, I always use the option --bitmap=internal.
>> With this option set, a bitmap is used to keep track of which pages on
>> the drive are out of date and then you only resync pages which need
>> updating instead of recopying the whole drive when this happens. In the
>> past I once added a bitmap to an existing raid1 array using something
>> like this. This may not be the exact command, but I know it can be done:
>> mdadm /dev/mdN --bitmap=internal
>>
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>>
>>     
>
>
>
> How do you add  --bitmap=internal to an existing, running RAID set? I
> have tried with the command above but got the following error:
>
>   
try mdadm /dev/md2 -Gb internal
also it pays to have everything clean first and check you have a 
persistent superblock
i.e. mdadm -D /dev/md2
HTH
> [root at intranet ~]# mdadm /dev/md2 --bitmap=internal
> mdadm: -b cannot have any extra immediately after it, sorry.
> [root at intranet ~]# cat /proc/mdstat
> Personalities : [raid1]
> md0 : active raid1 hda1[0]
>       104320 blocks [2/1] [U_]
>
> md2 : active raid1 sda1[0] sdb1[1]
>       244195904 blocks [2/2] [UU]
>
> md1 : active raid1 hda2[0]
>       244091520 blocks [2/1] [U_]
>
>
>
>
>   

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