[CentOS] Linux Software RAID 1 - Unequal Sized Hard Disks

Manish Kathuria mkathuria at tuxtechnologies.co.in
Thu Oct 18 12:53:28 EDT 2012

On Thu, Oct 18, 2012 at 9:02 PM, Reindl Harald <h.reindl at thelounge.net> wrote:
> Am 18.10.2012 17:29, schrieb Manish Kathuria:
>> Has anyone created or rebuilt a Linux Software RAID having mirrored
>> partitions on unequal sized hard disks ? There is  a CentOS 5 server
>> having two 400 GB hard disks with five mirrored partitions (software
>> RAID 1) and one of the hard disks is dying. Since new 400 GB HDDs are
>> not available here, we are exploring the possibility of replacing the
>> faulty hard disk with one of a higher capacity (500 GB or more). And
>> once it is fully replicated, we plan to replace the other 400 GB HDD
>> also with another hard disk of the same higher capacity.
>> Just want to know if anyone has done something similar and what are
>> the chances of success (or data loss) ?
> no problem at all
> * remove the disk
> * dd if=/dev/one-of-the-living/ of=/dev/new-disk/ bs=512 count=1
> * reboot or bring the kernel to re-read the partition table
> * rebuild the raid
> the dd-trick is intented to clone the complete partition table and
> MBR to the new disk and the additional space is untouched
> linux-software raid has no problem with different disk-sizes
> only the used partitions must be equal

Thanks Reindl, copying the first sector using is the simplest and
foolproof way of ensuring that the exact partition table is cloned but
would it also include the logical partitions ? In our case we have 5
partitions, two of which are logical ones.


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