Bruce,
Hot-spare drives can be global (available to any array on a controller) or dedicated (only usable by one array). There can be more than one hot spare per array and the drive of the closest capacity is used. If both dedicated and global hot-spare drives are available, then the dedicated drive is used first. If the hot swap rebuild fails, then that hot spare is also marked failed.
For more information see the RAID Software User's Guide.
Regards,
John
