Why do the indicators for HDD1 and HDD2 turn on and off repeatedly when the device is reading data during RAID1 creation for D2-310, D4-310, and D5-300C models?

When creating a RAID1 with HDD1 and HDD2, the data on both must be completely the same. Thus, when reading data, only HDD1 reads and writes; HDD2 remains in a waiting state, prolonging service life.