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Adaptec's port-aggregation software lets you make use of all of the redundant links as active connections (see diagram, below). To achieve this without proprietary hardware, Adaptec maintains only one full-duplex connection to the switch; the remaining connections must be half-duplex. In essence, you can have up to 12 ports in a single 1.2-Gbps "fat pipe" leading out of your server. However, the link back to the server is a single 100-Mbps connection. This scenario is good for client/server applications, but if your application involves equal amounts of reading and writing to the server, this solution may not yield much of a performance boost.
 In the lab, we were only able to push about 160 Mbps before maxing out the card. This appears to
be a limitation of the PCI bus or the card, not the CPU. Only one CPU was fully loaded, and the second showed 50 percent load. Officials from Adaptec said that we should expect improvements down the road.
The Adaptec solution starts at $399 for a two-port NIC. The DuraLink Failover drivers are available free from Adaptec; the DuraLink Port Aggregation software costs about $95. Drivers are available for Windows NT and Novell NetWare. We were impressed with the flexibility of the Adaptec solution and would recommend it for any site seeking resilient server connections.
·Intel EtherExpress PRO/100 Server Adapter The EtherExpress PRO/100 Server Adapter sports a power-packed Intel i960 on-board processor to improve system performance and supports advanced features like fault tolerance and Cisco ISL (InterSwitch Link) VLAN (virtual LAN) support. There are no hidden costs associated with the PRO/100 Server Adapter; its $599 price tag includes failover support and Cisco ISL VLAN support along with the i96
0 processor. And the PRO/100 Server adapter supports an MII (Media Independent Interface).
We tested the failover features of the PRO/100 Server adapter in our lab. Unlike the Adaptec DuraLink drivers, the Intel PRO/100 Server adapter supports only one active link at a time. After installing the adapter, you can configure it to be part of a fault-tolerant set. The PRO/100 drivers constantly monitor the active link for failure, and if the primary link fails, the backup adapter kicks in. We found that the Intel adapter consistently failed over in three to six seconds. Because the fault-tolerant drivers don't load-balance, Intel's fault-tolerant solution is also 100 percent standards-compliant. The adapter is capable of delivering 90 Mbps of bandwidth at 24 percent CPU utilization under Windows NT.
With its supports for Cisco's proprietary ISL VLAN tagging scheme, the card can actively participate in multiple VLANs. This is made possible by the i960 processor on the card. A future software update will supp
ort Intel's proprietary Adaptive Load Balancing algorithm and Cisco's Fast EtherChannel technology. Right now, however, you'll need two Intel adapters to get started, making this fault-tolerant solution a $1,200 investment. When the driver suite is complete, the Intel solution will offer a serious price advantage over competing Fast EtherChannel solutions.
·ZNYX RAINcluster ZX346ACS The RAINcluster puts a new spin on fault-tolerant networking. The RAINcluster (RAIN stands for Redundant Array of Independent Netports) is a fault-tolerant adapter built around Cisco's Fast EtherChannel technology. It's available as a two- or four-port card, which can be connected to any switch that supports Cisco's proprietary Fast EtherChannel technology. With Fast EtherChannel, up to four full-duplex, load-balancing connections can be made between the server and the switch. No other network adapter on the market can support multiple full-duplex connections to your infrastructure.
 We tested a beta version of the ZNYX RAINcluster using a Cisco Catalyst 2916M XL Fast Ethernet switch with a four-port Fast Ethernet channel. Recovery time when unplugging one or more of the Fast EtherChannel ports was less than one second. Unlike other products, the RAINcluster immediately resumes traffic when the cables are reconnected to the server. It too has an on-board i960 processor, which handles all load-balancing features. Engineers told us to expect more than 160 Mbps of throughput from the final product.
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