Spare drive and copy back mode

A drive mounted separately from the drives for usual write and read operation. When a drive fails, data stored in the failed drive is copied to the spare drive so that the storage system can continue to be available. If the copy back mode is enabled, data copied to the spare drive returns to the recovered drive. If the copy back mode is disabled, data copied to the spare drive still exists. This mode can be set to a parity group basis.

The maximum number of spare drives that can be specified for each storage system is as follows: