gmcpda-guard/how-to ? reverse-engineered prompt

Build me a simple, clear how to guide for creating a RAID 5 array with mdadm.

I want it written for someone who is comfortable using the terminal but does not want to guess any steps. Please make it easy to follow from start to finish, with the commands shown in order, plus a short explanation of what each step does. Include the usual setup checks, creating the array, formatting it, mounting it, saving it so it comes back after reboot, and a quick way to verify that it worked.

Please also add a small warning section about the risks of RAID 5 and data loss, since I want this to feel practical and safe. If any commands or details might depend on the current Linux docs, look them up online and use the current recommended approach. Keep it clean, readable, and focused on helping someone actually do it without getting stuck.