mdadm
Reference for managing Linux software RAID arrays with mdadm and the kernel md driver: creating arrays, persistent configuration, monitoring, disk failure recovery, write-intent bitmaps, and troubleshooting.
Mdadm
RAID
Reference for RAID levels 0, 1, 5, 6, and 10: redundancy, performance, hardware vs software RAID, rebuild and URE risk, scrubbing, cost comparison, and troubleshooting.