IBM Midrange System DS4000 Series Hardware Manual page 80

The DS5000 storage subsystem can attach up to 28 EXP5000s or EXP810s or a intermix of
the two for migration purposes. It also fully supports an intermix of the FC and SATA drives
inside enclosures to allow users maximum flexibility for customizing storage solutions. It is
generally best to spread enclosures evenly among the eights drive channel pairs as you scale
up your DS5000 storage subsystem's storage capacity. This allows you to fully utilize the
maximum drive-side bandwidth. For attaching the first four enclosures, use all the disk
channels, with one port per channel, as shown in Figure 3-35.
Figure 3-35 DS5000 with four disk enclosures
When attaching the next four enclosures, use the next ports in each channel, as shown in
Figure 3-36. For an eight enclosure configuration, each enclosure is attached to a dedicated
port pair.
Figure 3-36 DS5000 with eight disk enclosures
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IBM Midrange System Storage Hardware Guide