Well let me put it in a different way, the root volumes that i have along with data volumes on the same aggregate are our lab systems. I personally go with the best practices and so i recommend having root on a seperate aggregate. Yes, you can always move the root volume, but its just more work. I recommend doing it during the initial setup phase. If at all in future you want to move it, this is the procedure.
1. Disable the cluster: cf disable
2. Check the size of current vol0: vol size vol0
3. Create a new root volume on the SATA aggr: vol create vol0_new aggr0_sas <SIZE>
4. Copy the data to the new volume: ndmpcopy /vol/vol0 /vol/vol0_new
5. Rename the old root volume: vol rename vol0 vol0_old
6. Rename the new root volume: vol rename vol0_new vol0
7. Flag the new root volume as the root volume: vol options vol0 root
8. Reboot the controller: reboot
9. Confirm the SAS aggr now hosts the root vol0: aggr status on the left under Options it should say root on aggr0_sas
10. Offline and destroy the old volume vol0: vol offline vol0_old and vol destroy vol0_old
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