I created a few cluster resources but the "mount VOL_NAME VOLID=xxx" was
missing from the load script.

Do I need the "VOLID=xxx" portion?

It seems to work with just "mount VOL_NAME". I'm not sure if leaving the
VOLID out will cause any problems, or what exactly it's for.

If I do need it, how would I go about finding out what it should be?