Upgrade NAS540 from 2x1TB single volumes (no raid), to 4x2TB raid5

D4v3

I am looking to upgrade the disks in my NAS540. It is currently occupide by 2x1TB drvies as two single volumes (no raid). I want to build a raid5 volume out of four new 2TB disks. How would I go about doing this?
I had a plan to remove the two current disks, insert the new disks to build the new volume, and then using an external usb harddrive enclosure to connect the old drives via usb and copy the files to the new volume.  How ever upon removing disk1 and reconnecting it via usb as a trial run. the now external drive showed up as "unknown filesystem" in the NAS web interface. So how ever unexpected, it seems to be have been a bad plan.

Mijzelf

Although you now have 'single volumes' on that disks, the NAS still has put a raid array on them. A single disk raid1 array, when I remember well. The problem is that the NAS doesn't recognize raid arrays on external disks.

You have (at least) two options: You can assemble the array on the external disk manually in an ssh shell (I can provide instructions for that), or you can create your 4 disk array, pull one of the disks (making the array degraded), insert the old disks one by one, copy data over, and finally put the new 2TB disk back, and repair the volume.

Mijzelf

Although you now have 'single volumes' on that disks, the NAS still has put a raid array on them. A single disk raid1 array, when I remember well. The problem is that the NAS doesn't recognize raid arrays on external disks.

You have (at least) two options: You can assemble the array on the external disk manually in an ssh shell (I can provide instructions for that), or you can create your 4 disk array, pull one of the disks (making the array degraded), insert the old disks one by one, copy data over, and finally put the new 2TB disk back, and repair the volume.

D4v3

Ok, that explains the problem.
Thank you very much for the reply and solution.