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sometimes moves quickly to the CPU when servers are upgraded to incorporate
LANStreamer technology.
Of course, other components can emerge as the bottleneck as throughput
increases. The wire (network bandwidth) itself can become a bottleneck if
throughput requirements overwhelm the ability of the network technology being
used. For example, if an application requires 3 MBps of throughput, then a
token-ring at 16 Mbps will not perform the task. In this case a different network
technology must be employed.
For more discussion of hardware performance tuning, please see 5.1, “Hardware
Tuning” on page 167.
The LANStreamer technology is used in the IBM Auto LANStreamer Adapters for
PCI and MCA as well as the EtherStreamer and Dual EtherStreamer MC 32 LAN
adapters.
Note
The EtherStreamer LAN adapter supports full duplex mode, which allows the
adapter to transmit as well as receive at the same time. This provides an
effective throughput of 20 Mbps (10 Mbps on the receive channel and 10
Mbps on the transmit channel). To implement this feature, an external
switching unit is required.
1.7.3 PeerMaster Technology
The PeerMaster technology takes LAN adapters one step forward by
incorporating an on-board Intel i960 processor. This processing power is used to
implement per port switching on the adapter without the need for an external
switch. With this capability, frames can be switched between ports on the
adapter, bypassing the file server CPU totally.
If more than one card is installed, packets can be switched both intra- and
inter-card. The adapters utilize the Micro Channel to switch inter-card and can
transfer data at the very high speed of 640 Mbps.
The IBM Quad PeerMaster Adapter is a four-port Ethernet adapter which utilizes
this technology. It is a 32-bit Micro Channel bus master adapter capable of
utilizing the 80 MBps data streaming mode across the bus either to/from system
memory or peer to peer with another PeerMaster adapter.
It ships with 1MB of memory. Each port on an adapter serves a separate
Ethernet segment. Up to six of these adapters can reside on a single server and
up to 24 segments can be defined in a single server.
This adapter can also be used to create virtual networks (VNETs). Using VNETs,
the NOS sees multiple adapter ports as a single network, eliminating the need to
implement the traditional router function either internal or external to the file
server.
The Ethernet Quad PeerMaster Adapter is particularly appropriate when there is
a need for:
•
Switching/Bridging traffic among multiple Ethernet segments
•
Attaching more than eight Ethernet 10Base-T segments to the server
Chapter 1. IBM PC Server Technologies 33