Technical data

When the Memory Channel is set up in standard hub mode, the Memory
Channel hub must be visible to each member’s Memory Channel adapter.
If the hub is powered off, no system is able to boot.
A two-node cluster configured in virtual hub mode does not have these
problems. In virtual hub mode, each system is always connected to
the virtual hub. A loss of communication over the Memory Channel
causes both members (if both members are still up) to attempt to obtain
ownership of the quorum disk. The member that succeeds continues as a
single-member cluster. The other member panics.
A single system of a two-node cluster that is configured in virtual hub
mode will boot because a virtual hub is always present.
• If a TruCluster Server cluster configuration utilizes multiple Memory
Channel adapters in standard hub mode, the Memory Channel adapters
must be connected to separate Memory Channel hubs. The first Memory
Channel adapter (
mca0) in each system must be connected to one
Memory Channel hub. The second Memory Channel adapter (mcb0)in
each system must be connected to a second Memory Channel hub. Also,
each Memory Channel adapter on one system must be connected to the
same linecard in each Memory Channel hub.
• If redundant Memory Channel adapters are used with a DS10, they must
be jumpered for 128 MB and not the default of 512 MB.
• If you have redundant MC2 modules on a GS80, GS160, or GS320 system
jumpered for 512 MB, you cannot have any other modules except the
CCMFB fiber-optic module on that PCI bus.
• Redundant Memory Channels are supported within a mixed Memory
Channel configuration, as long as MC1 adapters are connected to other
MC1 adapters and MC2 adapters are connected to MC2 adapters.
In a cluster with mixed revision Memory Channel rails, the MC2 adapter
modules must be jumpered for 128 MB.
• A Memory Channel interconnect can use either virtual hub mode (two
member systems connected without a Memory Channel hub) or standard
hub mode (two or more systems connected to a hub). A TruCluster
Server cluster with three or more member systems must be jumpered for
standard hub mode and requires a Memory Channel hub.
• If Memory Channel modules are jumpered for virtual hub mode, all
Memory Channel modules on a system must be jumpered in the same
manner, either virtual hub 0 (VH0) or virtual hub 1 (VH1). You cannot
have one Memory Channel module jumpered for VH0 and another
jumpered for VH1 on the same system.
• The maximum length of an MC1 BC12N link cable is 3 meters (9.8 feet).
2–4 Hardware Requirements and Restrictions