Raid 5 to 6 is it do-able/safe?

Raid 5 to 6 is it do-able/safe?

[Jon Hardcastle]

Hi,

I run a 6 drive array with a multitude of drive sizes with 1 drive spare and 1 bay left.

I am running out of space! I want to take my drives past 1TB per drive (currently 500GB~1TB) but want RAID 6 for when the array goes to > 1TB per drive (coming soon)

I have deliberately kept 1 drive as a spare to give me the option of going to raid 6. Is this something mdadm can do? I have 

mdadm - v3.1.1 - 19th November 2009

I run gentoo with kernel 2.6.22-gentoo-r8

Don't know if it is relevant but have lvm on top

LVM version:     2.02.56(1) (2009-11-24)
Library version: 1.02.40 (2009-11-24)
Driver version:  4.11.0


I have seen talk on Neil's site, just not sure if the support is definately there.

If it is would i run something like this

mdadm --grow /dev/md4 --level=6 --raid-disk=7

to convert my 6 drive +1 spare raid 5 to a 7 drive raid 6? 


-----------------------
N: Jon Hardcastle
E: Jon@eHardcastle.com
'Do not worry about tomorrow, for tomorrow will bring worries of its own.'

***********
Please note, I am phasing out jd_hardcastle AT yahoo.com and replacing it with jon AT eHardcastle.com
***********

-----------------------


      

Re: Raid 5 to 6 is it do-able/safe?

[Mikael Abrahamsson]

On Tue, 29 Dec 2009, Jon Hardcastle wrote:

> I run gentoo with kernel 2.6.22-gentoo-r8
>
> to convert my 6 drive +1 spare raid 5 to a 7 drive raid 6?

No, you need at least kernel 2.6.32 to migrate from raid5 to raid6.

-- 
Mikael Abrahamsson    email: swmike@swm.pp.se

Re: Raid 5 to 6 is it do-able/safe?

[John Robinson]

On 29/12/2009 12:08, Mikael Abrahamsson wrote:
> On Tue, 29 Dec 2009, Jon Hardcastle wrote:
> 
>> I run gentoo with kernel 2.6.22-gentoo-r8
>>
>> to convert my 6 drive +1 spare raid 5 to a 7 drive raid 6?
> 
> No, you need at least kernel 2.6.32 to migrate from raid5 to raid6.

But if you don't want to run 2.6.32 permanently/on your live system, 
iirc you can just run it to do the migration, and once the migration and 
reshape have completed, you can go back to your production kernel.

Having said that, 2.6.22's a bit old and I don't see it listed on 
Gentoo's package web site, so you might think of updating to something 
more recent anyway.

Cheers,

John.

Re: Raid 5 to 6 is it do-able/safe?

[Kristleifur Daðason]

On Tue, Dec 29, 2009 at 1:31 PM, John Robinson
<john.robinson@anonymous.org.uk> wrote:
>
> On 29/12/2009 12:08, Mikael Abrahamsson wrote:
>>
>> On Tue, 29 Dec 2009, Jon Hardcastle wrote:
>>
>>> I run gentoo with kernel 2.6.22-gentoo-r8
>>>
>>> to convert my 6 drive +1 spare raid 5 to a 7 drive raid 6?
>>
>> No, you need at least kernel 2.6.32 to migrate from raid5 to raid6.
>
> But if you don't want to run 2.6.32 permanently/on your live system, iirc you can just run it to do the migration, and once the migration and reshape have completed, you can go back to your production kernel.
>

Besides the kernel version issues, this type of migration is
definitely possible and should be safe. I just did one of these before
christmas - grew a 3 or 4-disk RAID-5 into a 6-disk RAID-6, all on
1.5TB drives. Lots of fun nail-biting moments watching /proc/mdstat!
As it turned out, the thing just started, went about its business, and
finished in a quiet and refined manner. Now my arrays are vast and
comfortably redundant ...

Just give yourself a set of big, physical reminders to update your
mdadm.conf when the reshape / relevel is done.

And you really, preferably ought to back your data up before you do
this. Even though the rearrangement will probably work just fine.

Merry everything!

-- Kristleifur

Re: Raid 5 to 6 is it do-able/safe?

[Jon Hardcastle]

--- On Tue, 29/12/09, Mikael Abrahamsson <swmike@swm.pp.se> wrote:

> From: Mikael Abrahamsson <swmike@swm.pp.se>
> Subject: Re: Raid 5 to 6 is it do-able/safe?
> To: Jon@eHardcastle.com
> Cc: linux-raid@vger.kernel.org
> Date: Tuesday, 29 December, 2009, 12:08
> On Tue, 29 Dec 2009, Jon Hardcastle
> wrote:
> 
> > I run gentoo with kernel 2.6.22-gentoo-r8
> >
> > to convert my 6 drive +1 spare raid 5 to a 7 drive
> raid 6?
> 
> No, you need at least kernel 2.6.32 to migrate from raid5
> to raid6.
> 
> -- 
> Mikael Abrahamsson    email: swmike@swm.pp.se
> --
> To unsubscribe from this list: send the line "unsubscribe
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> 

Ok,

Cheers for your help guys! I have spent the week getting system/world up to date on my gentoo system and that included the kernel!

Unfortuntely the latest non-masked gentoo-sources kernel is 2.6.31-r7 which is what i now have are you certain it is .32 i need? I can get 2.6.32-r1 but it is masked currently.... anyone got an experience with this?

Cheers.


      
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Re: Raid 5 to 6 is it do-able/safe?

[Mikael Abrahamsson]

On Thu, 31 Dec 2009, Jon Hardcastle wrote:

> which is what i now have are you certain it is .32 i need? I can get

Yes, you need .32.

-- 
Mikael Abrahamsson    email: swmike@swm.pp.se