IBM eserver xSeries 440, User Manual

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Chapter 2. Configuring your server
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To connect the servers, note the following setup and configuration considerations:
• Make sure that the ASM interconnect network is set up as a bus, not as a ring.
You must connect the servers to the ASM interconnect network in a series, with
terminated beginning and end points.
• Make sure that the total combined length of all Ethernet cables connecting the
server in the ASM interconnect network does not exceed 91 M (300 ft).
• Each Remote Supervisor Adapter, ASM PCI adapter, or ASM processor that is
connected to the ASM interconnect network bus counts as one connection. For
example, if an ASM PCI adapter is installed in a server that has an ASM
processor, the processor and the adapter connect to each other using one ASM
interconnect connection, but the processor and the adapter count as two
connections on the ASM interconnect network bus.
Forwarding alerts:
Remote Supervisor Adapters, ASM PCI adapters, and ASM
processors that are connected to an ASM interconnect network share resources and
system-management information. This section provides information on how alerts are
forwarded in the ASM interconnect network.
During normal operation, each Remote Supervisor Adapter, ASM processor, or ASM
PCI adapter on the ASM interconnect network communicates with the other
processors and adapters on the network. Processors or adapters that have a modem
or Ethernet connection notify the other processors and adapters that these
communications resources are available for use by other servers on the ASM
interconnect network. These resources are then used as ASM interconnect network
resources, enabling Remote Supervisor Adapters, ASM processors, or ASM PCI
adapters on the ASM interconnect network to send alerts using a modem or the
network, even if they do not have a modem or network connection physically attached.
When alerts are generated, they are forwarded to the Remote Supervisor Adapter,
ASM processor, or ASM PCI adapter on the ASM interconnect network that has the
communication resources to forward the alert. If no system on the ASM interconnect
network meets the requirements, the alert is set for transmission if the connection type
is configured or becomes available later.
If multiple modems or network connections exist in the ASM interconnect network, you
cannot specify which system will receive an alert or which will use its modem or
network connection to forward the alert. If an alert is forwarded to a Remote
Supervisor Adapter, ASM processor, or ASM PCI adapter that is unable to deliver the
alert (for example, the modem it is configured to use has failed or the network cannot
resolve the destination IP address), the processor or adapter attempts to forward the
alert to another system on the ASM interconnect network that has the communication
resources to forward the alert.
Alerts are typically sent only once (per connection type), but an alert is forwarded to
another interconnect device if the resources exist on other interconnect devices in the
network. For example, on a three ASM processor network where ASM processor 1
generates a modem alert, but does not have a modem and the other ASM processors
have modems, the following might occur:
If ASM processor 1 generates an alert and the modem is unplugged from ASM
processor 2 45 seconds prior to ASM processor 1 generating the alert, ASM
processor 1 forwards the alert to ASM processor 2, having previously determined that
ASM processor 2 has an available modem. When ASM processor 2 receives the
forwarded alert, it determines that a modem is attached to ASM processor 3, and
forwards the alert. Therefore, depending upon the time frame (45 seconds) within
which a resource (modem) fails, the alert might be forwarded multiple times until an
interconnect device can send the alert.