Dell Broadcom NetXtreme Family of Adapters User Manual
Also see for Broadcom NetXtreme Family of Adapters: ManualUser guideInstallation
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Broadcom Teaming Services: Broadcom NetXtreme II Network Adapter User Guidefile:///T|/htdocs/NETWORK/BroadCom/71921/NetXtremeII/en/teamsvcs.htm[9/26/2012 3:29:14 PM]infrastructure must implement teaming such as load balancing and fault tolerance. Data centers will incorporate redundantswitches, link aggregation, and trunking as part of their fault tolerant solution. Although teaming device drivers willmanipulate the way data flows through teamed interfaces and failover paths, this is transparent to tape backup applicationsand does not interrupt any tape backup process when backing up remote systems over the network. Figure 10 shows anetwork topology that demonstrates tape backup in a Broadcom teamed environment and how smart load balancing can loadbalance tape backup data across teamed adapters.There are four paths that the client-server can use to send data to the backup server, but only one of these paths will bedesignated during data transfer. One possible path that Client-Server Red can use to send data to the backup server is:Example Path: Client-Server Red sends data through Adapter A, Switch 1, Backup Server Adapter A.The designated path is determined by two factors:Client-Server ARP cache; which points to the backup server MAC address. This is determined by the Broadcomintermediate driver inbound load balancing algorithm.The physical adapter interface on Client-Server Red will be used to transmit the data. The Broadcom intermediatedriver outbound load balancing algorithm determines this (see Outbound Traffic Flow and Inbound Traffic Flow (SLBOnly).The teamed interface on the backup server transmits a gratuitous address resolution protocol (G-ARP) to Client-Server Red,which in turn, causes the client server ARP cache to get updated with the Backup Server MAC address. The load balancingmechanism within the teamed interface determines the MAC address embedded in the G-ARP. The selected MAC address isessentially the destination for data transfer from the client server.On Client-Server Red, the SLB teaming algorithm willdetermine which of the two adapter interfaces will be used to transmit data. In this example, data from Client Server Red isreceived on the backup server Adapter A interface. To demonstrate the SLB mechanisms when additional load is placed on theteamed interface, consider the scenario when the backup server initiates a second backup operation: one to Client-ServerRed, and one to Client-Server Blue. The route that Client-Server Blue uses to send data to the backup server is dependant onits ARP cache, which points to the backup server MAC address. Because Adapter A of the backup server is already under loadfrom its backup operation with Client-Sever Red, the Backup Server invokes its SLB algorithm to inform Client-Server Blue(through an G-ARP) to update its ARP cache to reflect the backup server Adapter B MAC address. When Client-Server Blueneeds to transmit data, it uses either one of its adapter interfaces, which is determined by its own SLB algorithm. What isimportant is that data from Client-Server Blue is received by the Backup Server Adapter B interface, and not by its Adapter Ainterface. This is important because with both backup streams running simultaneously, the backup server must load balancedata streams from different clients. With both backup streams running, each adapter interface on the backup server isprocessing an equal load, thus load-balancing data across both adapter interfaces.The same algorithm applies if a third and fourth backup operation is initiated from the backup server. The teamed interfaceon the backup server transmits a unicast G-ARP to backup clients to inform them to update their ARP cache. Each client thentransmits backup data along a route to the target MAC address on the backup server.Fault ToleranceIf a network link fails during tape backup operations, all traffic between the backup server and client stops and backup jobsfail. If, however, the network topology was configured for both Broadcom SLB and switch fault tolerance, then this wouldallow tape backup operations to continue without interruption during the link failure. All failover processes within the networkare transparent to tape backup software applications. To understand how backup data streams are directed during networkfailover process, consider the topology in Figure 10. Client-Server Red is transmitting data to the backup server through Path1, but a link failure occurs between the backup server and the switch. Because the data can no longer be sent from Switch #1to the Adapter A interface on the backup server, the data is redirected from Switch #1 through Switch #2, to the Adapter Binterface on the backup server. This occurs without the knowledge of the backup application because all fault tolerantoperations are handled by the adapter team interface and trunk settings on the switches. From the client server perspective,it still operates as if it is transmitting data through the original path.Figure 10: Network Backup With SLB Teaming Across Two Switches |
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