On 08/04/17 22:42, LM wrote:

Hi,

I have a 4 disk RAID5, the used dev size is 640.05 GB. Now I want to
replace the 4 disks by 4 disks with a size of 2TB each.

As far as I understand the man page, this can be achieved by replacing
the devices one after another and for each device rebuild the degraded
array with:

   mdadm /dev/md0 --add /dev/sdX1

Do you have a spare SATA port or whatever your drives are. If so, then
use the --replace option to mdadm, don't fail then add. You're risking a
drive failure taking out your array - not a good move.

And if you don't have a spare port, $20 for a PCI card or whatever is a
good investment to keep your data safe.

Have a look at the raid wiki - it tries to be a bit more verbose and
easily comprehensible than the man page.

Cheers,
Wol