Hello,
Disk Spare should kick in irrespective of the enclosures,
However if it is a dedicated VDisk Spare, It'll kick in only if there is HDD Failure in the designated VDisk and will ot be a part of any VDIsk.
If set as Global Spare, Will kick in , in the event of failure of HDD in any VDisk , Provided the drive meets the parameters of the vdisk.
Hope this clarifies the query.
Regards
Shaan