Hi,  Yes, BCV's wont occupy any mirror position. So only 1 mirror position will be occupied in your case.
Hi,  I have a query around RVA and device mirror postions! I understand there are 4 mirror positions available and one position is only taken by a STD device as the RAID (e.g RAID 1) only takes up 1 mirror positon now which enables alot more scope for other activities such as migrating  a device a changing the RAID type at the same time.  I also understand that a STD with remote replication (SRDF) protection will occupy another position (and depending on the particular implementation of the RDF implemenation another e.g. Cascaded RDF hope am I right there). Also the likes of migrating a device uses another mirror position.  It is local replication which is confusing me. This should be managed by DDF sessions. So would a RAID1 STD device with two concurrent RAID1-BCVS established with it occupy 1 or 3 mirror positions? BCV is clone emulation in 5875 so the mirror positions should not come into the equation am I right?  Thanks, Victor  
RVA Mirror Position clarification