Extending an existing RAID (10) array

Extending an existing RAID (10) array

[cvb]

Hi, I have a short and hopefully simple question: On

https://raid.wiki.kernel.org/index.php/Growing

there is a section on expanding existing partitions. Does the procedure 
described there also apply to RAID 10 arrays?

I'm asking, because the section above says explicitly that it only 
applies to RAID level 1/4/5/6 arrays. The section on extending 
partitions is silent on that point...

I have a RAID 10 (software) array here, consisting of 4 disks. As one 
of the disks is a bit flaky, I'm thinking of replacing the (all) disks, 
maybe with bigger ones - if that should work.

Thanks, Chris

Re: Extending an existing RAID (10) array

[NeilBrown]

[-- Attachment #1: Type: text/plain, Size: 1005 bytes --]

On Wed, 03 Jul 2013 21:04:00 +0200 cvb@kruemel.org wrote:

> Hi, I have a short and hopefully simple question: On
> 
> https://raid.wiki.kernel.org/index.php/Growing
> 
> there is a section on expanding existing partitions. Does the procedure 
> described there also apply to RAID 10 arrays?
> 
> I'm asking, because the section above says explicitly that it only 
> applies to RAID level 1/4/5/6 arrays. The section on extending 
> partitions is silent on that point...
> 
> I have a RAID 10 (software) array here, consisting of 4 disks. As one 
> of the disks is a bit flaky, I'm thinking of replacing the (all) disks, 
> maybe with bigger ones - if that should work.
> 

There are two dimensions for growing an array - it is good to be explicit.
I think you are just talking about making the devices bigger without
increasing the number of devices.
This possible for RAID10 as long as it uses a 'near' or 'offset' layout.  It
is not support for 'far' layout RAID10.

NeilBrown

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 828 bytes --]

Re: Extending an existing RAID (10) array

[Christian]

On 04.07.2013 01:24, NeilBrown wrote:
> I think you are just talking about making the devices bigger without
> increasing the number of devices.
> This possible for RAID10 as long as it uses a 'near' or 'offset' layout.  It
> is not support for 'far' layout RAID10.

And as I just found out after some googling, growing RAID10 requires at 
least kernel 3.4rc. I have Ubuntu 12.04, which has kernel 3.2

I'm now thinking I could use a parted magic live cd to grow the array, 
and then continue using it with my current linux distribution. Am I 
right in this assumption? Or have I missed something?

Thanks, Chris

Re: Extending an existing RAID (10) array

[NeilBrown]

[-- Attachment #1: Type: text/plain, Size: 962 bytes --]

On Sun, 07 Jul 2013 08:33:19 +0200 Christian <CvB@kruemel.org> wrote:

> On 04.07.2013 01:24, NeilBrown wrote:
> > I think you are just talking about making the devices bigger without
> > increasing the number of devices.
> > This possible for RAID10 as long as it uses a 'near' or 'offset' layout.  It
> > is not support for 'far' layout RAID10.
> 
> And as I just found out after some googling, growing RAID10 requires at 
> least kernel 3.4rc. I have Ubuntu 12.04, which has kernel 3.2
> 
> I'm now thinking I could use a parted magic live cd to grow the array, 
> and then continue using it with my current linux distribution. Am I 
> right in this assumption? Or have I missed something?
> 
> Thanks, Chris

I don't know anything about parted magic live cds, but if you somehow boot
into a nice new kernel that supports resizing RAID10 arrays, and resize the
array and then go back to your old kernel, that should all work.

NeilBrown

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 828 bytes --]