please see my comments/answers in line beginning with ">>>"
The disks within dg should be scsi3-pr?
>>> Not really. e.g. JBOD. Howver, if you want to implement "FENCING", all the storage devices need to be SCSI-III PR compliant.
If they are not then on scsi bus reset the service group that contains that dg will fail over?
>>> Re=setting SCSI bus causes disks on the SCSI bus temporary offline. if you want to avoiid service group failover, you can freeze the service group with the dg that will be affected by SCSI bus re-set