RAID6 starts before RAID0 component - how to force the order?

RAID6 starts before RAID0 component - how to force the order?

[Trevor Cordes]

I'll keep this short and to the point and I'm hoping for a quick simple 
high-level answer from the gurus.  I don't need hand holding, so please 
take a quick look!

I have a new RAID6 array.  A component of that array is a RAID0 sub-array.  
mdadm creates and rebuilds this multilevel array just fine.  Then I 
reboot.  Boot log shows RAID6 detected first, _THEN_ RAID0.  Thus RAID6 is 
degraded without its RAID0 component.

The RAID0 array is fine/clean.  It's just a boot order problem I'm sure.

How do I set/force the order that arrays are started at boot time?  When 
doing multi-level arrays, you would think either a) you can force it or b) 
it would be "smart" about it.

FC3 kernel-2.6.12-1.1372_FC3
using mdadm
no raidtab

Thanks!

PS #1: if this is a mailing list, please CC my email.
PS #2: I did google searches for 2 hours and there is ZILCH on this topic

Re: RAID6 starts before RAID0 component - how to force the order?

[Tyler]

I only have a suggestion, not a definitive answer by any means.. but you 
may want to try the latest 2.6.13-rc3-mmX (or maybe rc4-mmX), I believe 
it has some changes in it, regarding the scanning and initialization of 
multi-level arrays.  I could be wrong though, but worth a shot in the 
day and age of 10 minute or less compiles :)

Tyler.

Trevor Cordes wrote:

>I'll keep this short and to the point and I'm hoping for a quick simple 
>high-level answer from the gurus.  I don't need hand holding, so please 
>take a quick look!
>
>I have a new RAID6 array.  A component of that array is a RAID0 sub-array.  
>mdadm creates and rebuilds this multilevel array just fine.  Then I 
>reboot.  Boot log shows RAID6 detected first, _THEN_ RAID0.  Thus RAID6 is 
>degraded without its RAID0 component.
>
>The RAID0 array is fine/clean.  It's just a boot order problem I'm sure.
>
>How do I set/force the order that arrays are started at boot time?  When 
>doing multi-level arrays, you would think either a) you can force it or b) 
>it would be "smart" about it.
>
>FC3 kernel-2.6.12-1.1372_FC3
>using mdadm
>no raidtab
>
>Thanks!
>
>PS #1: if this is a mailing list, please CC my email.
>PS #2: I did google searches for 2 hours and there is ZILCH on this topic
>-
>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: RAID6 starts before RAID0 component - how to force the order?

[Neil Brown]

On Friday August 5, trevor@tecnopolis.ca wrote:
> I'll keep this short and to the point and I'm hoping for a quick simple 
> high-level answer from the gurus.  I don't need hand holding, so please 
> take a quick look!
> 
> I have a new RAID6 array.  A component of that array is a RAID0 sub-array.  
> mdadm creates and rebuilds this multilevel array just fine.  Then I 
> reboot.  Boot log shows RAID6 detected first, _THEN_ RAID0.  Thus RAID6 is 
> degraded without its RAID0 component.
> 
> The RAID0 array is fine/clean.  It's just a boot order problem I'm sure.
> 
> How do I set/force the order that arrays are started at boot time?  When 
> doing multi-level arrays, you would think either a) you can force it or b) 
> it would be "smart" about it.

If you are depending on 'autodetect' with partition-type '0xfd', then
this won't work.
You should simply have mdadm assemble the arrays early in the boot
sequence.
If the raid0 is listed in mdadm before the raid6, then 
   mdadm -As
should assemble them in the correct order.

NeilBrown

> 
> FC3 kernel-2.6.12-1.1372_FC3
> using mdadm
> no raidtab
> 
> Thanks!
> 
> PS #1: if this is a mailing list, please CC my email.
> PS #2: I did google searches for 2 hours and there is ZILCH on this topic
> -
> 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