IBM System Storage DS4000, Hardware Manual

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Chapter 3. IBM System Storage DS4000 and DS5000 hardware
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Figure 3-33 Enclosure connections order
3.4.9 DS5100 and DS5300 storage subsystem drive-side cabling
The following rules apply while cabling the DS5000 with an expansion enclosure:
򐂰 The maximum number of expansion enclosures (EXP5000 or EXP810) in a drive loop is
limited to seven, as the maximum 112 disks limitation is reached with seven enclosures
configured with 16 drives each.
򐂰
Each FC-drive and expansion unit (EXP) in the drive channel must operate at the same
Fibre Channel speed (either 2 Gbps or 4 Gbps). SATA drives autonegotiate to the speed of
the EXP.
򐂰
The DS5000 controller drive port must always be connected to the EXP5000 port labelled
1B. Because the left and right EXP5000 ESMs (ESMs A and B) are inserted in the ESM
bays in different orientations, ensure that you use the port labeled 1B, as shown in
Figure 3-34. This applies to the previous DS4800 and DS4700 with its expansion units in
the same way. Port 1A is used to daisy-chain the next expansion units, which we refer to
later in this section
Figure 3-34 Port labels on EXP5000
Note: The numbering in Figure 3-33 is to help with the growth of a subsystem by adding
enclosures. It is not indicative of channel or port numbers.
Note: To achieve the best performance, spread all your expansion units among all port
channels.
1A
1B
1A 1B
Left ESM
Right ESM