A)
One disk fails during uptime, raid keeps running with 2 disks and on a reboot the array will get started through the --no-degraded or --incremental command with 2 disks.
B)
One disk fails during downtime, the array won't be started with --no-degraded or --incremental. A specific --run is necessary to start it degraded.
Example: 3 member mirroring array
A)
One disk fails during uptime, raid keeps running with 2 disks and on a reboot the array will get started through the --no-degraded or --incremental command with 2 disks.
B)
One disk fails during downtime, the array won't be started with --no-degraded or --incremental. A specific --run is necessary to start it degraded.