Preparing to move a RAID 5 array from one machine to another

Jimbo Mahoney · 24 Jun 2020 at 17:43

Hi all,

I've just set up a RAID 5 array using Raspbian / mdadm / webmin (using EXT4 if that makes any difference).

However, I'm aware that RAID can be very fragile and I want to prepare for when I reinstall the OS.

From some reading, I gather it *may* be as simple as just backing up the mdadm.conf file and then setting the RAID up again?

Luckily, at the moment, there is nothing on the array that I can't copy back again, so I can play around and "break" it during testing.

Also, is it normal to take 10 HOURS for the array to fully initialise? (I guess it might do when using USB drives and a Raspberry Pi?)

Jimbo Mahoney · 24 Jun 2020 at 18:28

Maybe as simple as this?

Code:

sudo mdadm --assemble --scan

EDIT - and possibly:

Code:

mdadm --detail --scan >> /etc/mdadm.conf

I'll give it a whirl...

Jimbo Mahoney · 25 Jun 2020 at 18:59

Just reinstalled the OS (raspbian) and mdadm.

It turns out that as long as I reconnect the two drives in the same USB ports, I don't need to do anything!

Rroff · 25 Jun 2020 at 19:12

I've had very mixed experiences moving RAID setups between systems - sometimes you can just plug it in and it works with a bit of initialising other times just a difference in controller firmware is a show stopper

SKILL · 1 Jul 2020 at 15:22

Was that hardware raid or mdadm?

I've used mdadm for several years and done I think 3 moves now, 2 planned 1 unplanned. Crossed different Linux distros as well as completely different hardware (all 3 different motherboards in the 4 setups, one was just a distro change) and for all I just needed the above "mdadm --assemble --scan", once a 'force' was required if a drive had failed (the unplanned was a motherboard/psu death that took one of the drives with it it seems

)

I was surprised over the years how seamless it was, for me at least