You cannot remove drives from the array - the number of disks must stay the same (or you can add to it). You would need to backup/restore to make a smaller VD. 
Hello. need some help. i have raid 5 build of 6 disks. 136GB x2 disks and 4 x 2 TB disks. ( why? don't ask some black out. ) raid controller perc 5/i  so a question is : can i safety ( without loosing data ) remove 2 disks of 136 GB and rebuild raid to work only with 4 disks of 2 TB and also volume to take all space?  
raid controller perc 5/i Raid 5 safety rebuid