I want to reconfigure my EX4100 to a RAID5 with 3x3TB. Is it possible to easily upgrade with a fourth 3TB hdd after several month without getting any data looses to the written data (on the existing raid5 configuration?). so basicly, is it possible to attach a fouth hdd to the (already configured) raid5? after restarting the nas, will it recognize the additional 3tb of storage? thx for ur answers 
Hello, thisisflo.
Yes, you can definitely add-up the 4th drive to the My cloud Ex4100 while the other Drive is in RAID5 configuration make sure that the Auto-Rebuild feature is turned on.
For more further information please Contact WD for Technical Support
