True,this can happen when there is no disk drive in the disk enclosure. The HSV controllers need a disk drive to talk to the EMU. In other case try swapping the EMU's, CAB cables, moving the CAB cable to a different posstion. You need to wait 1 or 2 minutes before you plug in the replacement EMU and it can take up to 8 minutes to recognize the new EMU.
Each disk enclosure has 2 I/O modules, one on each side. The cabling is done in two loops, to have redundancy. It should be like this:
Top controller - Enclosure 1 - Enclosure 2 ... - Bottom controller While on the other loop we reverse the order of the disk enclosures: Top controller ... Enclosure 2 - Enclosure 1 - Bottom controller.
Adding a new disk enclosure (up to 4 maximum) consists on inserting it on both loops. It can be done online if you open only one loop at a time.
You must also connect a cable to the EMU, the EAB cable, which allows the enclosure to know in what possition it is.
The enclosure must be added empty and then the disks added one by one with 2 minute interval between them. The minimum of disks on an enclosure is 4.
The EVA can work fine even when all disks are visible in the unmapped folder - one should not make any changes at that moment but give the EVA some time to recover.
