Re: Can I replace raid6 disk using dd?

[Ram Ramesh <rramesh2400@gmail.com>]

On 08/18/2014 09:30 PM, Ethan Wilson wrote:
> On 18/08/2014 21:26, Ram Ramesh wrote:
>> I had a recent disk failure in my 4x2TB raid6 and as a temporary fix I
>> added a 4tb drive to prevent the drive from being degraded while I
>> researched for a new drive.
>>
>> Now that I have purchased a new drive, I am wondering if it is ok to
>> simply dd the first 2tb of the 4tb drive to replace the drive. I am
>> asking because my case/motherboard does not have another HD slot to
>> add the new disk
>> in parallel with raid6. I was thinking of shutting down the machines,
>> moving the 4tb memmebr and the new drive to another machine, making
>> image copy (only 2tb), and putting the
>> 2tb drive back in the original machine and rebooting. Will this work?
>
>
> I think it should work, if metadata is 1.1 or 1.2 . I'm not sure if it 
> is 1.0 .
> You can also attach it via USB with an adapter, and do a replace (look 
> up "want_replacement") then shutdown, swap the drives, and turn on again.
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I thought about USB. First I do not have one, but that is a small 
problem to overcome. I was thinking more in terms of
performance. USB will slow things down as it is 2.0 (old MB) and dd 
should be real fast (130+ MB, based on the replacement)
But, I agree that mdadm replace is safer. Do I have to remove bitmap for 
replacement? I don't think so, but this is a newer operation and less 
info is available, so making sure.

Ramesh