Hi [NAME],   There is a chance of losing the data if the operating mode is being changed after the initial configuration.   Please refer to the below document (page 25) for more information.   [URL]
Ive had my R510 connected to an MD1220 for quite sometime and running stably.  I recently got 2 MD1200's to add to the rack.  I realized that my MD1220 has been in split mode, not unified.  It should be in Unified since it's run off a single PERC adapter host, right?  Will I lose my configuration or anything if I change the switch before a reboot?
R510 with Multiple PowerVaults