Special considerations exist for connecting the disk-drive enclosure
in a clustered environment. The information in this section will help you
meet these considerations.
Having any planning and cabling documentation for the system you are
attaching available during this process will make some parts of this process
much easier.
To assure that the SCSI disk-drive enclosure is ready
to be connected to the cluster complete the following steps.
- Ensure that each SCSI device connected to the shared SCSI bus has
a unique ID. A common configuration is to set the SCSI ID of the adapters
on the nodes to be higher than the SCSI IDs of the shared devices. (Devices
with higher IDs take precedence in SCSI bus contention.)
- Use the command: lscfg | grep scsi to determine
and record the logical name of each adapter. In the command
output, the first column lists the logical name of the SCSI adapter, such
as + SCSI0.
- Use the lscfg -vpl command and logical name
of the adapter to record the I/O slot (physical slot) that each SCSI adapter
uses. For example lscfg -vpl scsi0 where scsi0 is the logical
name of the adapter.
- Use the lsattr command, as in the following
example to find the ID of the adapter scsi0: lsattr -E -l scsi0 |
grep id
Note: Do not use wildcard characters or full pathnames
on the command line for the device name designation.
In
the resulting output, the first column lists the attribute names. The integer
to the right of the id attribute is the adapter SCSI ID:
If a SCSI adapter address conflict exists move on to the next
step, if no conflict exists return to the connection page for the operating
system of the system you are connecting.
- Examine the cabling to see if the proper ports on the system are
connected to the proper ports on the repeater cards on the disk-drive enclosure. For example if you are connecting the system using two host adapter
cards and dual repeater cards as shown in the following figure you will want
to connect the systems as follows.
Figure 1. SCSI cable
to dual repeater card connected with two SCSI cards
Cable the first SCSI bus or set of shared disks by doing the following:
- Connect the bottom port of the adapter on Host A (SCSI
address 7) to the exterior port on the repeater card in slot C2 on the enclosure.
- Connect the top port of the adapter on Host B (SCSI
address 6) to the exterior port on the repeater card in slot C3 on the enclosure.
This creates a set of shared disks and a shared SCSI bus (such as
scsi0) between Host A and Host B. The important thing to consider at this
point is that you connect the cables in descending order of the SCSI address
on the host adapter. Connecting the cables in descending order of the Host
SCSI address will reduce the potential for address conflicts.
Cable
the second SCSI bus or set of shared disks by doing the following:
- Connect the bottom port of the adapter on Host B (SCSI
address 7) to the interior port on the repeater card in slot C5 on the enclosure.
- Connect the top port of the adapter on Host A (SCSI
address 6) to the interior port on the repeater card in slot C4 on the enclosure.
This creates a set of shared disks and a shared SCSI bus (such as
scsi1) between Host A and Host B. The important thing to consider at this
point is that this is an independent SCSI bus or set of shared disks from
the first set. Ensuring that you do not mistakenly connect one of the cables
from the either SCSI bus to another will reduce the potential for SCSI address
conflicts.
Important: When adding, removing, or replacing
SCSI adapters in Host systems you might want to disconnect the cabling at
the enclosure first and reconnect the cabling to the enclosure last. This
is because the new adapter may default to a SCSI ID of 7. You should ensure
that the correct SCSI ID is set for the port you are cabling.
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