How to restore RAID MDADM if the system disk fails?

Question

linux

Hello. There is a system with a software fifth raid of 3 disks. The system itself with mdadm is installed on the 4th disk. The question arose, if the system disk fails, is that all? End? Or will it be possible to roll the system with mdadm onto a new disk and it will pick up the raid again? And in general, how are such systems properly organized? The system itself is also added to the raid?

Answer 1

Remain alive 5 raid. It can be pulled back. You will need to say a spell like mdadm --assemble --scan. More details in the documentation.
Such systems are properly organized by not using a single disk for the system. If you have 4 disks - raid6-10.

Answer 2

Much more interesting is what happens if one of those three disks fails, and at the time of the hellish load due to the rebuild, the second one.

Answer 3

Will pick up. The meta about the raid lies in the superblocks of the disks.