Controller Connections - IBM DS4800 User, Installation And Maintenance Manual

Figure 4 identifies the connectors on the back of each controller.
DC
power
Figure 4. Controller connections
Dual-ported drive channels
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IBM System Storage DS4800 Storage Subsystem: Installation, User's, and Maintenance Guide
Strain-relief
clamp
AC Dual-ported
power drive channels
Host channels
Ethernet ports
RS-232
serial port
Each controller has two drive channels; each drive channel has two fibre
channel ports. The drive channels are used to connect storage expansion
enclosures to the RAID controllers on the DS4800.
Note: Other DS4000 product documentation might refer to the drive
channel ports as "expansion ports."
Attention: The DS4800 requires the attachment of at least one DS4000
storage expansion enclosure populated with at least two drives to be
operational. Without being connected to at least one DS4000 storage
expansion enclosure populated with at least two drives, the DS4800
controller will not successfully complete the power-on process.
Two drive channels (one from each controller) are used to form a redundant
drive channel pair. Each drive channel pair supports up to a maximum of
112 drives in seven or eight IBM DS4000 storage expansion enclosures,
depending on the enclosure types. (SeeTable 3 on page 9 for more
information.)
The drive channel port speeds are auto-negotiated between 2 Gbps and 4
Gbps fibre channel speeds. Both ports of a dual-ported drive channel must
be connected to storage expansion enclosures operating at the same fibre
channel speed. In addition, link-speed negotiation for a given port is limited
to the link speeds supported by the Small Form-factor Pluggable (SFP)
module plugged in that port.
However, if the 2 Gbps and the 4 Gbps DS4000 storage expansion
enclosures are separated into different redundant drive channel pairs, the
DS4800 ( 1 ) will support both 2 Gbps and the 4 Gbps DS4000 storage
expansion enclosures at their own fibre channel speed (either 2 Gbps or 4
Gbps). For example, as shown in Figure 5 on page 13, the redundant drive
RS-232
Ethernet ports serial port
Controller A
Host channels
Controller B
AC
power DC
Dual-ported
drive channels
Strain-relief
clamp
power