A RAID 6 write is 3 read and 3 write disk operations. A SATA disk can do around 50 IOPS. You can multiply out the number of disks and host writes (plus reads) to work out how capable your SATA tier is.  For RAID 1, it is 2 disk writes per write and for RAID 5, its 2 reads and 2 writes per host write.  An FC 10K is capable of around 120 IOPS and a 15K around 150 IOPS.  It's just a case of taking the IOPS rating of the disk, applying the RAID overhead to the read / write ratio and host IOPS to see how busy your tier will be from a host IOPS perspective.  e.g. Your host is bound to (RAID 6) SATA and does 120 writes and 50 read miss per second. 120*6+50=770. 770(disk IOPS) / 50(SATA rating) = 16 SATA disks required to support the workload. Compare this to a RAID 1 FC pool: 120*2+50=290. 290/120=2.5 You need way less FC disk from a performance perspective in this example and supports the earlier comments that the FC tier is typically best practice as the tier for the initial bind. You should be able to use the above to make an infiormed decision on where do bind your devices to.  Don't forget there can be  other overheads on the disk: - FAST movement - Local replication - Drive failures
I have created 10 devices and bound to FC pool with FAST policy 100-100-100, What difference does it make if I bound to SATA pool and associate same FAST policy of 100-100-100??
FAST and Bound to pool