Is there any difference between the monthly parity check one might schedule as a maintenance task or a data rebuild when one replaces a disk? When you replace a failed disk, does it not do a parity check while it's doing the data rebuild?

I am not sure that the question even makes sense if you understand parity?

 

the monthly check is assuming that the array disks are OK and that the parity is correct for their contents.

 

a rebuild assumes that parity is correct and uses the contents of the parity drive plus all the remaining data drives to reconstruct what should be on the failed drive.   At this point there is no check running as with a failed drive this is not possible.