Re: raid1 w/ 3 active mirrors?

[Laurent CARON <lcaron@apartia.fr>]

Gordon Mohr (@ Bitzi) a écrit :

> Michael Tokarev wrote:
>
>> Gordon Mohr (@ Bitzi) wrote:
>>
>>> I may have missed this is various docs, but is there any way to make
>>> a raid1 array which has 3 (or more) active mirrors, rather than 2 
>>> mirrors
>>> and spares?
>>
>>
>>
>> On our machines with software raid, I usually use all available disks to
>> create (small) root filesystem on raid1 - which is 2, 3, 4, 5, or even 8
>> on one machine.  There's no special restriction on number of mirrors in
>> a raid1 set.  You create raid1 array on top of N disks exactly the same
>> as you create it on 2 disks.
>
>
> How do you make all the disks active mirrors? When I add a third 
> partition
> to an functioning RAID1 array (mdadm -a), it always enters as a 
> 'spare'. Only
> after another disk fails out will it be brought into sync with the 
> remaining
> active partition.
>
> (I'd like the third partition to be brought into sync, and kept in sync,
> with the other two immediately, so that a fail does not trigger any
> flurry of activity.)
>
> Thanks,
>
> - Gordon @ Bitzi
> -
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when you create the array:

mdadm -Cv /dev/md0 -l1 -n10 /dev/sd{a,b,c,d,e,f,g,h,i,j}1

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