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Chapter 2. Components 31
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.
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.
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.