I have a new QNAP TS-451 NAS with two new 3TB drives, installed as a RAID 1 pair. As I copy data on to it, it seems to spend the next few hours "synchronizing" the RAID group. (The web console shows a status like "Synchronizing (4.3%)")
Why is this? What prevents the system simultaneously writing to both disks at once, keeping the RAID group constantly synchronized?
(I'm not sure if this is on-topic here, and I don't know if this is a QNAP-specific issue.)