raid1 w/ 3 active mirrors?

raid1 w/ 3 active mirrors?

[Gordon Mohr (@ Bitzi)]

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?

Thanks for any tips,

- Gordon @ Bitzi

Re: raid1 w/ 3 active mirrors?

[Michael Tokarev]

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.

/mjt

Re: raid1 w/ 3 active mirrors?

[Gordon Mohr (@ Bitzi)]

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

Re: raid1 w/ 3 active mirrors?

[Laurent CARON]

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
> -
> 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

when you create the array:

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

-- 
La morale c'est l'ensemble des règles que l'on trouve excellentes pour
autrui et inutile pour soi.
	-+- Voltaire -+-

-
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

Re: raid1 w/ 3 active mirrors?

[Gordon Mohr (@ Bitzi)]

Laurent CARON wrote:
> Gordon Mohr (@ Bitzi) a écrit :

>> 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.)

> when you create the array:
> 
> mdadm -Cv /dev/md0 -l1 -n10 /dev/sd{a,b,c,d,e,f,g,h,i,j}1

Thanks for the tip.

I'm hoping to do this to a prexisting array, so I'll probably need
to use --grow rather than -C together with -n/--raid-devices, but
you've pointed me in the right direction and I'll try this soon.

Merci!

- Gordon @ Bitzi
-
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