Reshaping the length of devices

Reshaping the length of devices

[Asdo]

I am wondering... is it possible to reshape the length of the underlying 
devices with MD raid?

I mean like in the case one buys larger disks: after moving the raid 
partitions to the new disks half of them is still free. So one might 
want to extend the raid partitions to the end of the disks instead of 
creating another array in the free space.

I have searched the linux-raid mailing list history but I couldn't find 
this topic.

Thanks in advance

Re: Reshaping the length of devices

[Jon Hardcastle]

--- On Fri, 12/3/10, Asdo <asdo@shiftmail.org> wrote:

> From: Asdo <asdo@shiftmail.org>
> Subject: Reshaping the length of devices
> To: "linux-raid" <linux-raid@vger.kernel.org>
> Date: Friday, 12 March, 2010, 15:15
> I am wondering... is it possible to
> reshape the length of the underlying devices with MD raid?
> 
> I mean like in the case one buys larger disks: after moving
> the raid partitions to the new disks half of them is still
> free. So one might want to extend the raid partitions to the
> end of the disks instead of creating another array in the
> free space.
> 
> I have searched the linux-raid mailing list history but I
> couldn't find this topic.
> 
> Thanks in advance

As long as the size of ALL underlying devices have increased you can --grow=MAX to the a multiple of the now smallest drive.

From:

http://linux.die.net/man/8/mdadm

This value can be set with --grow for RAID level 1/4/5/6. If the array was created with a size smaller than the currently active drives, the extra space can be accessed using --grow. The size can be given as max  which means to choose the largest size that fits on all current drives. 


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

***********
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***********

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


      

Re: Reshaping the length of devices

[John Robinson]

On 12/03/2010 15:18, Jon Hardcastle wrote:
> 
> 
> --- On Fri, 12/3/10, Asdo <asdo@shiftmail.org> wrote:
> 
>> From: Asdo <asdo@shiftmail.org>
>> Subject: Reshaping the length of devices
>> To: "linux-raid" <linux-raid@vger.kernel.org>
>> Date: Friday, 12 March, 2010, 15:15
>> I am wondering... is it possible to
>> reshape the length of the underlying devices with MD raid?
>>
>> I mean like in the case one buys larger disks: after moving
>> the raid partitions to the new disks half of them is still
>> free. So one might want to extend the raid partitions to the
>> end of the disks instead of creating another array in the
>> free space.
>>
>> I have searched the linux-raid mailing list history but I
>> couldn't find this topic.
>>
>> Thanks in advance
> 
> As long as the size of ALL underlying devices have increased you can --grow=MAX to the a multiple of the now smallest drive.

Hmm, that reminds me I was meaning to ask - before I have to go to a 
customer's premises and try it - if I have a CentOS 5 system with 0.90 
metadata and type fd partitions with RAID-5 over 3 discs, and I want to 
grow it by replacing the drives, if I dd small partitions onto larger 
ones and reboot, will the system recognise the RAID-5 - which now has 
its metadata somewhere in the middle of the paritions not at the end - 
so that I can then --grow?

Cheers,

John.

Re: Reshaping the length of devices

[Majed B.]

John, don't hijack the thread.

Post your question in a separate email.

On Fri, Mar 12, 2010 at 7:54 PM, John Robinson
<john.robinson@anonymous.org.uk> wrote:
> On 12/03/2010 15:18, Jon Hardcastle wrote:
>>
>>
>> --- On Fri, 12/3/10, Asdo <asdo@shiftmail.org> wrote:
>>
>>> From: Asdo <asdo@shiftmail.org>
>>> Subject: Reshaping the length of devices
>>> To: "linux-raid" <linux-raid@vger.kernel.org>
>>> Date: Friday, 12 March, 2010, 15:15
>>> I am wondering... is it possible to
>>> reshape the length of the underlying devices with MD raid?
>>>
>>> I mean like in the case one buys larger disks: after moving
>>> the raid partitions to the new disks half of them is still
>>> free. So one might want to extend the raid partitions to the
>>> end of the disks instead of creating another array in the
>>> free space.
>>>
>>> I have searched the linux-raid mailing list history but I
>>> couldn't find this topic.
>>>
>>> Thanks in advance
>>
>> As long as the size of ALL underlying devices have increased you can
>> --grow=MAX to the a multiple of the now smallest drive.
>
> Hmm, that reminds me I was meaning to ask - before I have to go to a
> customer's premises and try it - if I have a CentOS 5 system with 0.90
> metadata and type fd partitions with RAID-5 over 3 discs, and I want to grow
> it by replacing the drives, if I dd small partitions onto larger ones and
> reboot, will the system recognise the RAID-5 - which now has its metadata
> somewhere in the middle of the paritions not at the end - so that I can then
> --grow?
>
> Cheers,
>
> John.
> --
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>



-- 
       Majed B.
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Re: Reshaping the length of devices

[John Robinson]

On 12/03/2010 17:08, Majed B. wrote:
> John, don't hijack the thread.
> 
> Post your question in a separate email.

Well, I didn't think I was wildly off-topic for the thread, but OK.

Cheers,

John.

Re: Reshaping the length of devices

[Majed B.]

I think it depends on how you migrate to the new disks. The best
option would be to have one partition use all the space on the new
(larger) disks, and replace a disk in the array with the new disk &
wait for it to sync. Do the same for all disks.

You'll end up with a working array, where each disk has 1 partition
but the total size of the array is only consuming half the capacity.

After that just use --growth and it'll expand the array to the max
available capacity from the disks.

On Fri, Mar 12, 2010 at 6:15 PM, Asdo <asdo@shiftmail.org> wrote:
> I am wondering... is it possible to reshape the length of the underlying
> devices with MD raid?
>
> I mean like in the case one buys larger disks: after moving the raid
> partitions to the new disks half of them is still free. So one might want to
> extend the raid partitions to the end of the disks instead of creating
> another array in the free space.
>
> I have searched the linux-raid mailing list history but I couldn't find this
> topic.
>
> Thanks in advance
> --
> 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
>



-- 
       Majed B.
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