In this post, https://community.emc.com/thread/143811?start=0&tstart=0, ksnell said the following...

When enabling FAST Cache you reported a degradation in IOPs for the workload. With analysis, we observed the FAST Cache drives running at 100% utilization, around 9K IOPs, with over 90% of those IOPs being writes

Where in EMC Analyser can we see the utilization of the FAST Cache disks?