SCSI Solutions White Paper - HP-UX

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and disconnects the BCC from the enclosure’s internal bus, thus effectively isolating the
BCC whose HBA has been disconnected from the rest of the bus and the other BCC.
6. DS2300 termination: Each BCC in the DS2300, whether in split-bus or full-bus
mode, acts like a separate SCSI bus with respect to termination, and thus any unused
port of a BCC whose other port is connected to an HBA must be physically terminated.
See also section 3.1.2.
7. Online Repairability: Online Replacement (OLR) of an HBA is only supported in
configurations in which the physical disconnection of the SCSI cable from the HBA to
the bus will not result in instability of the bus (which can lead to data corruption, bus
hangs, and other problems). Thus, HBA OLR is supported in single-initiator
configurations. It is also supported in dual-initiator configurations on the DS2300 in
which each initiator is attached to a separate BCC. Only one port on each DS2300
BCC can be connected to a host because disconnecting an HBA from one port on a
BCC will bring the other port down. As a result, the DS2300 must be configured in
full-bus mode to allow both hosts to see all the disks and thus allow continuous data
availability across the OLR operation.
Full multi-initiator configurations, with initiators connected to all four SCSI ports, are
supported on the MSA30 MI. This is a result of its auto-termination capabilities which
auto-terminate the port when the cable is disconnected.
Use of ILT cables (on Ultra or lower speed buses), as discussed in 3.1.3, allows only for
online disconnection and not subsequent reconnection.
8. Configurations without online repairability: Configurations which meet the
other shared bus requirements but which don’t meet the above requirements for online
repairability can be supported without online repairability. In such cases, all initiators
connected to the shared bus must be halted and power removed from the bus before
any portion of the SCSI bus can be disconnected.
9. Root/Boot disks: root/boot disks can be on a SCSI bus that is shared across
multiple hosts as long as the shared bus only contains active root/boot disks for a single
host. This is because boot firmware does not support two nodes booting from the same
SCSI bus at the same time. Note: mirroring of root/boot to another bus that contains
the root/boot disks of another host is allowed.