Have you ever unplugged the wrong drive and then had to rebuild the entire array? It may not be a big deal in some ways but it does make your system vulnerable until the rebuild is done. Many distros often enable the "bitmap" feature and this basically keeps track of what parts need to be resynced in the case of a temporary removal of a drive from the array, this way it only needs to sync what has changed. To enable bitmap to speed up rebuilds and sync........

I separated the 2 drives in the RAID 1 array. 1 is the old one /dev/sda and is out of date, while the separated other one /dev/sdc was in another drive and mounted and used with more data (updated). I wonder how mdadm will handle this: usb-storage: device scan complete md: md127 stopped. md: bind md: md127: raid array is not clean -- starting background reconstruction raid1: raid set md127 active with 1 out of 2 m........

md: Autodetecting RAID arrays. md: autorun ... md: considering sdb1 ... md: adding sdb1 ... md: adding sda1 ... md: created md0 md: bind md: bind md: running: md: kicking non-fresh sda1 from array! md: unbind md: export_rdev(sda1) raid1: raid set md0 active with 1 out of 2 mirrors The md0 raid kicked sda1 ou........