Disk not detected equallogic PS4100

I have an equalogic ps4100 that have 12 disks with the size of 3 TB per disk, but only 6 disks detectable. The setting for the configuration that I set were group, ip address, raid policy and member only. When i login via the web, only 6 disks detectable, I've tried to reset the configuration from the beginning then changed the raid policy but the results are still the same (6 disks unable to detected). Is the disk broken? Or is there any configuration that I missed?