IBM manual Disk enclosures, DS8000 device adapter

integrity it supports metadata creation and checking. The device adapter design is shown in Figure 2-8.

Figure 2-8 DS8000 device adapter

The DAs are installed in pairs because each storage partition requires its own adapter to connect to each disk enclosure for redundancy. This is why we refer to them as DA pairs.

2.4.2 Disk enclosures

Each DS8000 frame contains either 8 or 16 disk enclosures depending on whether it is a base or expansion frame. Half of the disk enclosures are accessed from the front of the frame, and half from the rear. Each DS8000 disk enclosure contains a total of 16 DDMs or dummy carriers. A dummy carrier looks very similar to a DDM in appearance but contains no electronics. The enclosure is pictured in Figure 2-9 on page 32.

Note: If a DDM is not present, its slot must be occupied by a dummy carrier. This is because without a drive or a dummy, cooling air does not circulate correctly.

Each DDM is an industry standard FC-AL disk. Each disk plugs into the disk enclosure backplane. The backplane is the electronic and physical backbone of the disk enclosure.

Chapter 2. Components 31