I have a RAID5 array that consists of 3, 2TB drives. I want to add 2 more drives. The tutorials involve adding a single drive to an array, such as this:
https://raid.wiki.kernel.org/index.php/Growing
Can I add both drives at the same time? Can I do something like (going by the example in the wiki):
mdadm --add /dev/md1 /dev/sdb3 /dev/sdb4
mdadm --grow --raid-devices=5 /dev/md1
Or is it better to just add a single drive at a time?
Best Answer
Your array isn't any more vulnerable during 1 disk or 2 disk grow, there's only a small critical section in which a power outage can destroy the array.
Considering, that growing by 2 disks at once will finish much faster, I'd suggest going this way, there's no downside to it that I know of.