[CentOS] RAIDs and JBOD?

John R Pierce pierce at hogranch.com
Wed Nov 11 00:27:04 UTC 2009

James Bensley wrote:
> I have read a few articles about mdadm and I have devised the
> following strategy in my head and am looking for some confirmation of
> its theoretical success:
> Two of my existing three drives are full of data. I will purchase two
> more drives to go with my existing blank drive and set them up as a
> RAID 5 > copy my existing data on to the new file system one drive at
> a time and after each drive has been copied I will add said drive and
> use mdadm --grow to then incorporate that drive into the RAID before
> adding the next drive. Can anyone point out a flaw in this plan or
> more preferred method for doing this, or have I, dare I say it, got it
> right?

growing raid-5 by adding drives is an inherently dangerous operation as 
every single stripe of the raid has to be reorganized, and can take 
hours or even days.


I prefer wherever possible to build a new raid, copy the data, and when 
I'm assured the copy is correct, re purpose the old drives.

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