When a disk is in the maintenance center, it is subjected to a number of tests. If the disk passes all of the tests, it is redesignated as a spare. Otherwise, Data ONTAP fails the disk.
The maintenance center is controlled by the disk.maint_center.enable option. It is on by default.
Data ONTAP puts disks into the maintenance center only if there are two or more spares available for that disk.
You can control the number of times a disk is allowed to go to the maintenance center using the disk.maint_center.allowed_entries option. The default value for this option is 1, which means that if the disk is ever sent back to the maintenance center, it is automatically failed.
You can also put a disk into the maintenance center manually by using the disk maint start command. If the target disk is in use, it does not enter the maintenance center until its contents have been copied to another disk (unless you include the -i option).
You can see the power-cycle status for ESH4 disk shelves by using the environment shelf_power_status command.
For information about best practices for working with the maintenance center, see Technical Report 3437: Storage Best Practices and Resiliency Guide.