Replace disk in RAID10 for root partition

Hi, I bought a dedicated server yesterday with 4 HDDs which I configured in RAID 10 (this is softraid) with just swap, boot and root (/) partitions. I am looking for info on what to do if a disk fails so to be prepared, and I have found one page in the docs that talks about this but the examples are for the /home partition, which can be unmounted while running the commands in the live system. However I have everything in a single "/" partition for simplicity, so it's a different configuration. How do I proceed in this case? I guess I cannot unmount the root partition on a live system? I have never tried it so I am not sure. Thanks!