[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.

--
Manish


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