I'm not sure IO generated that way will have a skew of active vs. inactive data.  RAID1 for the FC tier as a best practice has been documented many places.  This tier is a IOPs tier.  You want the cheapest IOPs/$$ and RAID1 will give you that.  RAID5 will cost more per IOP, as long as there are writes in the workload.  FAST VP doesn't take RAID protection into account, but it does look at utilization of the tiers/drives and won't promote onto overloaded tiers.
So we are FINALLY cruising along in our VMAX 20K testing but i'm a little concerned with FAST VP SATA usage.  I’ve been testing a pretty heavy SQL workload over the past week from two servers in FAST VP.  If I run both at the same time it will peak to about 48K IOPS.  In our configuration we have 16 EFD in R5, 388 10K FC in R5, and 280 SATA in R6.  The SATA is broken up into two disk groups due to using some for the vault, but both SATA disk groups are in the same pool.  My concern is when I put a storage group in a policy that allows 100% on any tier it doesn’t seem to use FC much at all, although it does put a small percentage in EFD.  In fact I moved a SG entirely to FC and FAST VP demoted down to SATA pretty quickly even while I was running jobs.  I also tried binding to FC since the SG's were origionally binded to SATA but with the “Allocate by FAST policy” enabled in 5876 it will put new writes to the tier that it thinks it should where in 5875 all new writes went to whatever teir it was binded to. My assumption from reading "Implementing Fully Automated Storage Tiering for Virtual Pools (FAST VP) for EMC Symmetrix VMAX Series Arrays Technical Notes" would be I/O in FC should be higher than SATA I’m seeing 6K IOPS in two SATA Disk Groups for a total of 12K in SATA and only 600 IOPS in the FC.  SATA seems to be handling it fine now, but we only have 24TB out of 510TB allocated so I’m worried what will happen with this SATA tier once we go live and start migrating a bunch of hosts.  Also with SATA being R6 having a lot of I/O there really hits the director CPUs due to the dual parity.  With only two hosts and this I/O i've seen the directors average 55-65% utilization.  Hosts are using one FA on each director for a total of 8.  Also the two hosts that are on here are not sharing an FA.  One server is on all E0 ports and the other is on all F0 ports.  Has anyone seen this SATA utilization at all in their environment and have any thoughts?    Also, what is everyones thoughts on the relocation rate?  Keep it conservative at 7 or more aggressive?  Thanks
FAST VP SATA usage and relocation rate