Connecting Hosts To The Ds4800 - IBM DS4800 User, Installation And Maintenance Manual

The DS4800 normally ships with an enclosure ID outside the range of 00–77.
However, if your DS4800 enclosure ID was set to a value within the range of
00–77, it may be in conflict with the enclosure ID of one of the EXP100 or EXP710
drive expansion enclosures that you are trying to attach to the DS4800. If this is the
case, the amber ID Conflict LED on the storage expansion enclosure will light after
you power on the storage subsystem.
Give each storage expansion enclosure in a redundant drive channel pair a unique
ones digit (x1) ID. This setting will enforce hard AL_PAs (unchangeable between
fibre channel Loop Initializations [LIPs]) for the drives and facilitate drive channel
problem troubleshooting in the event of an error. If the ones digits are not unique,
two or more devices will have the same hard AL_PA. In such a case, the DS4800
controller will use soft AL_PAs for the devices that have identical hard AL_PAs.
The problem with soft addressing is that addresses may change between LIPs. This
possibility increases the difficulty of troubleshooting drive channel problems, since
one cannot easily ascertain whether the same device with a different address or
different device may be causing a problem.

Connecting hosts to the DS4800

The DS4800 supports redundant connections to up to four hosts. To ensure full
protection against the loss of any one fibre channel path from the host servers to
the DS4800 Storage Subsystem, always use redundant host connections by
connecting each host to the appropriate single-ported host channels on both RAID
controllers A and B.
To connect a host adapter to the DS4800 RAID controllers, perform the following
steps:
1. Install SFP modules in host ports on RAID controllers A and B.
2. Connect the fibre channel cables from the SFP modules in the DS4800 RAID
Note: The alignment of the single-ported host channels on controller A are
opposite those of controller B. Before inserting an SFP module into a
host port, verify that the SFP module is rotated correctly to match the
alignment of the host port on the RAID controller. Do not force-fit.
controller host ports to either the SFP modules in the fibre channel switch or the
SFP modules of the host bus adapters. Figure 58 on page 80 shows the
location on the RAID controllers where the host-system cables connect.
Chapter 3. Cabling the storage subsystem
79