Re-size RAID-10

Re-size RAID-10

[Daniel L. Miller]

I think I asked this once before, if so I apologize for the redundancy - 
but then again maybe something's changed...

I've got a RAID-10 array with four drives.  It's nearing capacity, and I 
need to explore expansion options.  Can I simply add a pair of new 
drives?  Or do I have to archive the information first and rebuild the 
array from scratch?

-- 
Daniel

Re: Re-size RAID-10

[Neil Brown]

On Wednesday March 25, dmiller@amfes.com wrote:
> I think I asked this once before, if so I apologize for the redundancy - 
> but then again maybe something's changed...
> 
> I've got a RAID-10 array with four drives.  It's nearing capacity, and I 
> need to explore expansion options.  Can I simply add a pair of new 
> drives?  Or do I have to archive the information first and rebuild the 
> array from scratch?

It is not currently possible to resize a raid-10.

NeilBrown

Re: Re-size RAID-10

[Raz]

Neil Hello
I will be grateful for your reply. Currently I am working on raid0
code reshape.
 1. Will you be working on this functionality in the near future ?
 2. Should I save the superblocks like mdadm does in the case of 1,4,5,6 ?
 3. What is the heuristics of strip_zones ? why do we need them ?

. non-power 2 raid0 chunk sizes.
 4. Other than segments masks issues, why isn't possible ? can't i fix raid0
  to support 3MB chunks with a segment of 1MB ?

Thank you

On Thu, Mar 26, 2009 at 12:14 AM, Neil Brown <neilb@suse.de> wrote:
> On Wednesday March 25, dmiller@amfes.com wrote:
>> I think I asked this once before, if so I apologize for the redundancy -
>> but then again maybe something's changed...
>>
>> I've got a RAID-10 array with four drives.  It's nearing capacity, and I
>> need to explore expansion options.  Can I simply add a pair of new
>> drives?  Or do I have to archive the information first and rebuild the
>> array from scratch?
>
> It is not currently possible to resize a raid-10.
>
> NeilBrown
>
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Re: Re-size RAID-10

[Keld Jørn Simonsen]

On Thu, Mar 26, 2009 at 09:14:22AM +1100, Neil Brown wrote:
> On Wednesday March 25, dmiller@amfes.com wrote:
> > I think I asked this once before, if so I apologize for the redundancy - 
> > but then again maybe something's changed...
> > 
> > I've got a RAID-10 array with four drives.  It's nearing capacity, and I 
> > need to explore expansion options.  Can I simply add a pair of new 
> > drives?  Or do I have to archive the information first and rebuild the 
> > array from scratch?
> 
> It is not currently possible to resize a raid-10.

In my mind, it should not be that difficult, tho, to do it.

Is resize an operation that needs to be done with the fs unmounted?

best regards
keld

Re: Re-size RAID-10

[Raz]

2009/3/26 Keld Jørn Simonsen <keld@dkuug.dk>:
> On Thu, Mar 26, 2009 at 09:14:22AM +1100, Neil Brown wrote:
>> On Wednesday March 25, dmiller@amfes.com wrote:
>> > I think I asked this once before, if so I apologize for the redundancy -
>> > but then again maybe something's changed...
>> >
>> > I've got a RAID-10 array with four drives.  It's nearing capacity, and I
>> > need to explore expansion options.  Can I simply add a pair of new
>> > drives?  Or do I have to archive the information first and rebuild the
>> > array from scratch?
>>
>> It is not currently possible to resize a raid-10.
>
> In my mind, it should not be that difficult, tho, to do it.
>
> Is resize an operation that needs to be done with the fs unmounted?
No. in raid5 there is no need for that.
> best regards
> keld
>
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>
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Re: Re-size RAID-10

[Neil Brown]

On Thursday March 26, raziebe@gmail.com wrote:
> Neil Hello
> I will be grateful for your reply. Currently I am working on raid0
> code reshape.
>  1. Will you be working on this functionality in the near future ?

I have no plans for raid0 reshape or raid10 reshape.

>  2. Should I save the superblocks like mdadm does in the case of 1,4,5,6 ?

When the layout changes, you certainly have to update the superblock,
yes.


>  3. What is the heuristics of strip_zones ? why do we need them ?

To make maximum use of available space.

> 
> . non-power 2 raid0 chunk sizes.
>  4. Other than segments masks issues, why isn't possible ? can't i fix raid0
>   to support 3MB chunks with a segment of 1MB ?

There is no intrinsic reason why chunk sizes should be powers of two.
When I started working on the code that limit already existed and I
have never had any reason to remove it.

If you would like to create patches which provide support for
non-power-of-two chunk sizes, I will be happy to review them.

NeilBrown