Question about converting CIFS FS to ISCSI for MS Exchange Data

I am running an NS500 with CX-500 attached storage. I have 2 files systems -1 ISCSI for MS Exchange and the other are a couple CIFS Filesystems which are used for myWindows Fileserver. I am migrating off the CIFS File system because I'm about out of space and the shelf is full. My ISCSI MS Exchange disks are experiencing a good deal of latency lately and performance is taking a hit. Couple of questions:

The main one is, can I delete the CIFS Filesystems and create new a ISCSI one to move some Exchange data to? This will free up Disk I/O on the current ISCSI FS.

Also, my only concern with this is that the disks I would be converting to ISCSI are RAID5 and that is not ideal for Exchange DB's. But I would only be moving Public folders (less than 100GB). MS recommends RAID1 which is what my current Exchange data is on.
Basically I trying to weigh out if overall performance for exchange will be better. I'd be moving PF DB"s to a completely separate shelf of disks (15K FC) but not RAID1. I've talked to EMC and these drives cannot be built with RAID1 because the first 5 drives run the entire system.

Thanks